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javascript replace backslashes with forward slashes on path [duplicate]

Given a string:
s = "Test abc test test abc test test test abc test test abc";
This seems to only remove the first occurrence of abc in the string above:
s = s.replace('abc', '');
How do I replace all occurrences of it?

As of August 2020: Modern browsers have support for the String.replaceAll() method defined by the ECMAScript 2021 language specification.
For older/legacy browsers:
function escapeRegExp(string) {
return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}
function replaceAll(str, find, replace) {
return str.replace(new RegExp(escapeRegExp(find), 'g'), replace);
}
Here is how this answer evolved:
str = str.replace(/abc/g, '');
In response to comment "what's if 'abc' is passed as a variable?":
var find = 'abc';
var re = new RegExp(find, 'g');
str = str.replace(re, '');
In response to Click Upvote's comment, you could simplify it even more:
function replaceAll(str, find, replace) {
return str.replace(new RegExp(find, 'g'), replace);
}
Note: Regular expressions contain special (meta) characters, and as such it is dangerous to blindly pass an argument in the find function above without pre-processing it to escape those characters. This is covered in the Mozilla Developer Network's JavaScript Guide on Regular Expressions, where they present the following utility function (which has changed at least twice since this answer was originally written, so make sure to check the MDN site for potential updates):
function escapeRegExp(string) {
return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}
So in order to make the replaceAll() function above safer, it could be modified to the following if you also include escapeRegExp:
function replaceAll(str, find, replace) {
return str.replace(new RegExp(escapeRegExp(find), 'g'), replace);
}

For the sake of completeness, I got to thinking about which method I should use to do this. There are basically two ways to do this as suggested by the other answers on this page.
Note: In general, extending the built-in prototypes in JavaScript is generally not recommended. I am providing as extensions on the String prototype simply for purposes of illustration, showing different implementations of a hypothetical standard method on the String built-in prototype.
Regular Expression Based Implementation
String.prototype.replaceAll = function(search, replacement) {
var target = this;
return target.replace(new RegExp(search, 'g'), replacement);
};
Split and Join (Functional) Implementation
String.prototype.replaceAll = function(search, replacement) {
var target = this;
return target.split(search).join(replacement);
};
Not knowing too much about how regular expressions work behind the scenes in terms of efficiency, I tended to lean toward the split and join implementation in the past without thinking about performance. When I did wonder which was more efficient, and by what margin, I used it as an excuse to find out.
On my Chrome Windows 8 machine, the regular expression based implementation is the fastest, with the split and join implementation being 53% slower. Meaning the regular expressions are twice as fast for the lorem ipsum input I used.
Check out this benchmark running these two implementations against each other.
As noted in the comment below by #ThomasLeduc and others, there could be an issue with the regular expression-based implementation if search contains certain characters which are reserved as special characters in regular expressions. The implementation assumes that the caller will escape the string beforehand or will only pass strings that are without the characters in the table in Regular Expressions (MDN).
MDN also provides an implementation to escape our strings. It would be nice if this was also standardized as RegExp.escape(str), but alas, it does not exist:
function escapeRegExp(str) {
return str.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"); // $& means the whole matched string
}
We could call escapeRegExp within our String.prototype.replaceAll implementation, however, I'm not sure how much this will affect the performance (potentially even for strings for which the escape is not needed, like all alphanumeric strings).

In the latest versions of most popular browsers, you can use replaceAll
as shown here:
let result = "1 abc 2 abc 3".replaceAll("abc", "xyz");
// `result` is "1 xyz 2 xyz 3"
But check Can I use or another compatibility table first to make sure the browsers you're targeting have added support for it first.
For Node.js and compatibility with older/non-current browsers:
Note: Don't use the following solution in performance critical code.
As an alternative to regular expressions for a simple literal string, you could use
str = "Test abc test test abc test...".split("abc").join("");
The general pattern is
str.split(search).join(replacement)
This used to be faster in some cases than using replaceAll and a regular expression, but that doesn't seem to be the case anymore in modern browsers.
Benchmark: https://jsben.ch/TZYzj
Conclusion:
If you have a performance-critical use case (e.g., processing hundreds of strings), use the regular expression method. But for most typical use cases, this is well worth not having to worry about special characters.

Here's a string prototype function based on the accepted answer:
String.prototype.replaceAll = function(find, replace) {
var str = this;
return str.replace(new RegExp(find, 'g'), replace);
};
If your find contains special characters then you need to escape them:
String.prototype.replaceAll = function(find, replace) {
var str = this;
return str.replace(new RegExp(find.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&'), 'g'), replace);
};
Fiddle: http://jsfiddle.net/cdbzL/

Use word boundaries (\b)
'a cat is not a caterpillar'.replace(/\bcat\b/gi,'dog');
//"a dog is not a caterpillar"
This is a simple regex that avoids replacing parts of words in most cases. However, a dash - is still considered a word boundary. So conditionals can be used in this case to avoid replacing strings like cool-cat:
'a cat is not a cool-cat'.replace(/\bcat\b/gi,'dog');//wrong
//"a dog is not a cool-dog" -- nips
'a cat is not a cool-cat'.replace(/(?:\b([^-]))cat(?:\b([^-]))/gi,'$1dog$2');
//"a dog is not a cool-cat"
Basically, this question is the same as the question here:
Replace " ' " with " '' " in JavaScript
Regexp isn't the only way to replace multiple occurrences of a substring, far from it. Think flexible, think split!
var newText = "the cat looks like a cat".split('cat').join('dog');
Alternatively, to prevent replacing word parts—which the approved answer will do, too! You can get around this issue using regular expressions that are, I admit, somewhat more complex and as an upshot of that, a tad slower, too:
var regText = "the cat looks like a cat".replace(/(?:(^|[^a-z]))(([^a-z]*)(?=cat)cat)(?![a-z])/gi,"$1dog");
The output is the same as the accepted answer, however, using the /cat/g expression on this string:
var oops = 'the cat looks like a cat, not a caterpillar or coolcat'.replace(/cat/g,'dog');
//returns "the dog looks like a dog, not a dogerpillar or cooldog" ??
Oops indeed, this probably isn't what you want. What is, then? IMHO, a regex that only replaces 'cat' conditionally (i.e., not part of a word), like so:
var caterpillar = 'the cat looks like a cat, not a caterpillar or coolcat'.replace(/(?:(^|[^a-z]))(([^a-z]*)(?=cat)cat)(?![a-z])/gi,"$1dog");
//return "the dog looks like a dog, not a caterpillar or coolcat"
My guess is, this meets your needs. It's not foolproof, of course, but it should be enough to get you started. I'd recommend reading some more on these pages. This'll prove useful in perfecting this expression to meet your specific needs.
RegExp (regular expression) object
Regular-Expressions.info
Here is an example of .replace used with a callback function. In this case, it dramatically simplifies the expression and provides even more flexibility, like replacing with correct capitalisation or replacing both cat and cats in one go:
'Two cats are not 1 Cat! They\'re just cool-cats, you caterpillar'
.replace(/(^|.\b)(cat)(s?\b.|$)/gi,function(all,char1,cat,char2)
{
// Check 1st, capitalize if required
var replacement = (cat.charAt(0) === 'C' ? 'D' : 'd') + 'og';
if (char1 === ' ' && char2 === 's')
{ // Replace plurals, too
cat = replacement + 's';
}
else
{ // Do not replace if dashes are matched
cat = char1 === '-' || char2 === '-' ? cat : replacement;
}
return char1 + cat + char2;//return replacement string
});
//returns:
//Two dogs are not 1 Dog! They're just cool-cats, you caterpillar

These are the most common and readable methods.
var str = "Test abc test test abc test test test abc test test abc"
Method 1:
str = str.replace(/abc/g, "replaced text");
Method 2:
str = str.split("abc").join("replaced text");
Method 3:
str = str.replace(new RegExp("abc", "g"), "replaced text");
Method 4:
while(str.includes("abc")){
str = str.replace("abc", "replaced text");
}
Output:
console.log(str);
// Test replaced text test test replaced text test test test replaced text test test replaced text

Match against a global regular expression:
anotherString = someString.replace(/cat/g, 'dog');

For replacing a single time, use:
var res = str.replace('abc', "");
For replacing multiple times, use:
var res = str.replace(/abc/g, "");

str = str.replace(/abc/g, '');
Or try the replaceAll method, as recommended in this answer:
str = str.replaceAll('abc', '');
or:
var search = 'abc';
str = str.replaceAll(search, '');
EDIT: Clarification about replaceAll availability
The replaceAll method is added to String's prototype. This means it will be available for all string objects/literals.
Example:
var output = "test this".replaceAll('this', 'that'); // output is 'test that'.
output = output.replaceAll('that', 'this'); // output is 'test this'

Using RegExp in JavaScript could do the job for you. Just simply do something like below code, and don't forget the /g after which standout for global:
var str ="Test abc test test abc test test test abc test test abc";
str = str.replace(/abc/g, '');
If you think of reuse, create a function to do that for you, but it's not recommended as it's only one line function. But again, if you heavily use this, you can write something like this:
String.prototype.replaceAll = String.prototype.replaceAll || function(string, replaced) {
return this.replace(new RegExp(string, 'g'), replaced);
};
And simply use it in your code over and over like below:
var str ="Test abc test test abc test test test abc test test abc";
str = str.replaceAll('abc', '');
But as I mention earlier, it won't make a huge difference in terms of lines to be written or performance. Only caching the function may affect some faster performance on long strings and is also a good practice of DRY code if you want to reuse.

Say you want to replace all the 'abc' with 'x':
let some_str = 'abc def def lom abc abc def'.split('abc').join('x')
console.log(some_str) //x def def lom x x def
I was trying to think about something more simple than modifying the string prototype.

Use a regular expression:
str.replace(/abc/g, '');

Performance
Today 27.12.2019 I perform tests on macOS v10.13.6 (High Sierra) for the chosen solutions.
Conclusions
The str.replace(/abc/g, ''); (C) is a good cross-browser fast solution for all strings.
Solutions based on split-join (A,B) or replace (C,D) are fast
Solutions based on while (E,F,G,H) are slow - usually ~4 times slower for small strings and about ~3000 times (!) slower for long strings
The recurrence solutions (RA,RB) are slow and do not work for long strings
I also create my own solution. It looks like currently it is the shortest one which does the question job:
str.split`abc`.join``
str = "Test abc test test abc test test test abc test test abc";
str = str.split`abc`.join``
console.log(str);
Details
The tests were performed on Chrome 79.0, Safari 13.0.4 and Firefox 71.0 (64 bit). The tests RA and RB use recursion. Results
Short string - 55 characters
You can run tests on your machine HERE. Results for Chrome:
Long string: 275 000 characters
The recursive solutions RA and RB gives
RangeError: Maximum call stack size exceeded
For 1M characters they even break Chrome
I try to perform tests for 1M characters for other solutions, but E,F,G,H takes so much time that browser ask me to break script so I shrink test string to 275K characters. You can run tests on your machine HERE. Results for Chrome
Code used in tests
var t="Test abc test test abc test test test abc test test abc"; // .repeat(5000)
var log = (version,result) => console.log(`${version}: ${result}`);
function A(str) {
return str.split('abc').join('');
}
function B(str) {
return str.split`abc`.join``; // my proposition
}
function C(str) {
return str.replace(/abc/g, '');
}
function D(str) {
return str.replace(new RegExp("abc", "g"), '');
}
function E(str) {
while (str.indexOf('abc') !== -1) { str = str.replace('abc', ''); }
return str;
}
function F(str) {
while (str.indexOf('abc') !== -1) { str = str.replace(/abc/, ''); }
return str;
}
function G(str) {
while(str.includes("abc")) { str = str.replace('abc', ''); }
return str;
}
// src: https://stackoverflow.com/a/56989553/860099
function H(str)
{
let i = -1
let find = 'abc';
let newToken = '';
if (!str)
{
if ((str == null) && (find == null)) return newToken;
return str;
}
while ((
i = str.indexOf(
find, i >= 0 ? i + newToken.length : 0
)) !== -1
)
{
str = str.substring(0, i) +
newToken +
str.substring(i + find.length);
}
return str;
}
// src: https://stackoverflow.com/a/22870785/860099
function RA(string, prevstring) {
var omit = 'abc';
var place = '';
if (prevstring && string === prevstring)
return string;
prevstring = string.replace(omit, place);
return RA(prevstring, string)
}
// src: https://stackoverflow.com/a/26107132/860099
function RB(str) {
var find = 'abc';
var replace = '';
var i = str.indexOf(find);
if (i > -1){
str = str.replace(find, replace);
i = i + replace.length;
var st2 = str.substring(i);
if(st2.indexOf(find) > -1){
str = str.substring(0,i) + RB(st2, find, replace);
}
}
return str;
}
log('A ', A(t));
log('B ', B(t));
log('C ', C(t));
log('D ', D(t));
log('E ', E(t));
log('F ', F(t));
log('G ', G(t));
log('H ', H(t));
log('RA', RA(t)); // use reccurence
log('RB', RB(t)); // use reccurence
<p style="color:red">This snippet only presents codes used in tests. It not perform test itself!<p>

Replacing single quotes:
function JavaScriptEncode(text){
text = text.replace(/'/g,''')
// More encode here if required
return text;
}

Using
str = str.replace(new RegExp("abc", 'g'), "");
worked better for me than the previous answers. So new RegExp("abc", 'g') creates a regular expression what matches all occurrences ('g' flag) of the text ("abc"). The second part is what gets replaced to, in your case empty string ("").
str is the string, and we have to override it, as replace(...) just returns result, but not overrides. In some cases you might want to use that.

This is the fastest version that doesn't use regular expressions.
Revised jsperf
replaceAll = function(string, omit, place, prevstring) {
if (prevstring && string === prevstring)
return string;
prevstring = string.replace(omit, place);
return replaceAll(prevstring, omit, place, string)
}
It is almost twice as fast as the split and join method.
As pointed out in a comment here, this will not work if your omit variable contains place, as in: replaceAll("string", "s", "ss"), because it will always be able to replace another occurrence of the word.
There is another jsperf with variants on my recursive replace that go even faster (http://jsperf.com/replace-all-vs-split-join/12)!
Update July 27th 2017: It looks like RegExp now has the fastest performance in the recently released Chrome 59.

Loop it until number occurrences comes to 0, like this:
function replaceAll(find, replace, str) {
while (str.indexOf(find) > -1) {
str = str.replace(find, replace);
}
return str;
}

If what you want to find is already in a string, and you don't have a regex escaper handy, you can use join/split:
function replaceMulti(haystack, needle, replacement)
{
return haystack.split(needle).join(replacement);
}
someString = 'the cat looks like a cat';
console.log(replaceMulti(someString, 'cat', 'dog'));

function replaceAll(str, find, replace) {
var i = str.indexOf(find);
if (i > -1){
str = str.replace(find, replace);
i = i + replace.length;
var st2 = str.substring(i);
if(st2.indexOf(find) > -1){
str = str.substring(0,i) + replaceAll(st2, find, replace);
}
}
return str;
}

I like this method (it looks a little cleaner):
text = text.replace(new RegExp("cat","g"), "dog");

String.prototype.replaceAll - ECMAScript 2021
The new String.prototype.replaceAll() method returns a new string with all matches of a pattern replaced by a replacement. The pattern can be either a string or a RegExp, and the replacement can be either a string or a function to be called for each match.
const message = 'dog barks meow meow';
const messageFormatted = message.replaceAll('meow', 'woof')
console.log(messageFormatted);

Of course in 2021 the right answer is:
String.prototype.replaceAll()
console.log(
'Change this and this for me'.replaceAll('this','that') // Normal case
);
console.log(
'aaaaaa'.replaceAll('aa','a') // Challenged case
);
If you don't want to deal with replace() + RegExp.
But what if the browser is from before 2020?
In this case we need polyfill (forcing older browsers to support new features) (I think for a few years will be necessary).
I could not find a completely right method in answers. So I suggest this function that will be defined as a polyfill.
My suggested options for replaceAll polyfill:
replaceAll polyfill (with global-flag error) (more principled version)
if (!String.prototype.replaceAll) { // Check if the native function not exist
Object.defineProperty(String.prototype, 'replaceAll', { // Define replaceAll as a prototype for (Mother/Any) String
configurable: true, writable: true, enumerable: false, // Editable & non-enumerable property (As it should be)
value: function(search, replace) { // Set the function by closest input names (For good info in consoles)
return this.replace( // Using native String.prototype.replace()
Object.prototype.toString.call(search) === '[object RegExp]' // IsRegExp?
? search.global // Is the RegEx global?
? search // So pass it
: function(){throw new TypeError('replaceAll called with a non-global RegExp argument')}() // If not throw an error
: RegExp(String(search).replace(/[.^$*+?()[{|\\]/g, "\\$&"), "g"), // Replace all reserved characters with '\' then make a global 'g' RegExp
replace); // passing second argument
}
});
}
replaceAll polyfill (With handling global-flag missing by itself) (my first preference) - Why?
if (!String.prototype.replaceAll) { // Check if the native function not exist
Object.defineProperty(String.prototype, 'replaceAll', { // Define replaceAll as a prototype for (Mother/Any) String
configurable: true, writable: true, enumerable: false, // Editable & non-enumerable property (As it should be)
value: function(search, replace) { // Set the function by closest input names (For good info in consoles)
return this.replace( // Using native String.prototype.replace()
Object.prototype.toString.call(search) === '[object RegExp]' // IsRegExp?
? search.global // Is the RegEx global?
? search // So pass it
: RegExp(search.source, /\/([a-z]*)$/.exec(search.toString())[1] + 'g') // If not, make a global clone from the RegEx
: RegExp(String(search).replace(/[.^$*+?()[{|\\]/g, "\\$&"), "g"), // Replace all reserved characters with '\' then make a global 'g' RegExp
replace); // passing second argument
}
});
}
Minified (my first preference):
if(!String.prototype.replaceAll){Object.defineProperty(String.prototype,'replaceAll',{configurable:!0,writable:!0,enumerable:!1,value:function(search,replace){return this.replace(Object.prototype.toString.call(search)==='[object RegExp]'?search.global?search:RegExp(search.source,/\/([a-z]*)$/.exec(search.toString())[1]+'g'):RegExp(String(search).replace(/[.^$*+?()[{|\\]/g,"\\$&"),"g"),replace)}})}
Try it:
if(!String.prototype.replaceAll){Object.defineProperty(String.prototype,'replaceAll',{configurable:!0,writable:!0,enumerable:!1,value:function(search,replace){return this.replace(Object.prototype.toString.call(search)==='[object RegExp]'?search.global?search:RegExp(search.source,/\/([a-z]*)$/.exec(search.toString())[1]+'g'):RegExp(String(search).replace(/[.^$*+?()[{|\\]/g,"\\$&"),"g"),replace)}})}
console.log(
'Change this and this for me'.replaceAll('this','that')
); // Change that and that for me
console.log(
'aaaaaa'.replaceAll('aa','a')
); // aaa
console.log(
'{} (*) (*) (RegEx) (*) (\*) (\\*) [reserved characters]'.replaceAll('(*)','X')
); // {} X X (RegEx) X X (\*) [reserved characters]
console.log(
'How (replace) (XX) with $1?'.replaceAll(/(xx)/gi,'$$1')
); // How (replace) ($1) with $1?
console.log(
'Here is some numbers 1234567890 1000000 123123.'.replaceAll(/\d+/g,'***')
); // Here is some numbers *** *** *** and need to be replaced.
console.log(
'Remove numbers under 233: 236 229 711 200 5'.replaceAll(/\d+/g, function(m) {
return parseFloat(m) < 233 ? '' : m
})
); // Remove numbers under 233: 236 711
console.log(
'null'.replaceAll(null,'x')
); // x
// The difference between My first preference and the original:
// Now in 2022 with browsers > 2020 it should throw an error (But possible it be changed in future)
// console.log(
// 'xyz ABC abc ABC abc xyz'.replaceAll(/abc/i,'')
// );
// Browsers < 2020:
// xyz xyz
// Browsers > 2020
// TypeError: String.prototype.replaceAll called with a non-global RegExp
Browser support:
Internet Explorer 9 and later (rested on Internet Explorer 11).
All other browsers (after 2012).
The result is the same as the native replaceAll in case of the first argument input is:
null, undefined, Object, Function, Date, ... , RegExp, Number, String, ...
Ref: 22.1.3.19 String.prototype.replaceAll ( searchValue, replaceValue)
+ RegExp Syntax
Important note: As some professionals mention it, many of recursive functions that suggested in answers, will return the wrong result. (Try them with the challenged case of the above snippet.)
Maybe some tricky methods like .split('searchValue').join('replaceValue') or some well managed functions give same result, but definitely with much lower performance than native replaceAll() / polyfill replaceAll() / replace() + RegExp
Other methods of polyfill assignment
Naive, but supports even older browsers (be better to avoid)
For example, we can support IE7+ too, by not using Object.defineProperty() and using my old naive assignment method:
if (!String.prototype.replaceAll) {
String.prototype.replaceAll = function(search, replace) { // <-- Naive method for assignment
// ... (Polyfill code Here)
}
}
And it should work well for basic uses on IE7+.
But as here #sebastian-simon explained about, that can make secondary problems in case of more advanced uses. E.g.:
for (var k in 'hi') console.log(k);
// 0
// 1
// replaceAll <-- ?
Fully trustable, but heavy
In fact, my suggested option is a little optimistic. Like we trusted the environment (browser and Node.js), it is definitely for around 2012-2021. Also it is a standard/famous one, so it does not require any special consideration.
But there can be even older browsers or some unexpected problems, and polyfills still can support and solve more possible environment problems. So in case we need the maximum support that is possible, we can use polyfill libraries like:
https://polyfill.io/
Specially for replaceAll:
<script src="https://polyfill.io/v3/polyfill.min.js?features=String.prototype.replaceAll"></script>

The simplest way to do this without using any regular expression is split and join, like the code here:
var str = "Test abc test test abc test test test abc test test abc";
console.log(str.split('abc').join(''));

var str = "ff ff f f a de def";
str = str.replace(/f/g,'');
alert(str);
http://jsfiddle.net/ANHR9/

while (str.indexOf('abc') !== -1)
{
str = str.replace('abc', '');
}

If the string contains a similar pattern like abccc, you can use this:
str.replace(/abc(\s|$)/g, "")

As of August 2020 there is a Stage 4 proposal to ECMAScript that adds the replaceAll method to String.
It's now supported in Chrome 85+, Edge 85+, Firefox 77+, Safari 13.1+.
The usage is the same as the replace method:
String.prototype.replaceAll(searchValue, replaceValue)
Here's an example usage:
'Test abc test test abc test.'.replaceAll('abc', 'foo'); // -> 'Test foo test test foo test.'
It's supported in most modern browsers, but there exist polyfills:
core-js
es-shims
It is supported in the V8 engine behind an experimental flag --harmony-string-replaceall.
Read more on the V8 website.

The previous answers are way too complicated. Just use the replace function like this:
str.replace(/your_regex_pattern/g, replacement_string);
Example:
var str = "Test abc test test abc test test test abc test test abc";
var res = str.replace(/[abc]+/g, "");
console.log(res);

After several trials and a lot of fails, I found that the below function seems to be the best all-rounder when it comes to browser compatibility and ease of use. This is the only working solution for older browsers that I found. (Yes, even though old browser are discouraged and outdated, some legacy applications still make heavy use of OLE browsers (such as old Visual Basic 6 applications or Excel .xlsm macros with forms.)
Anyway, here's the simple function.
function replaceAll(str, match, replacement){
return str.split(match).join(replacement);
}

If you are trying to ensure that the string you are looking for won't exist even after the replacement, you need to use a loop.
For example:
var str = 'test aabcbc';
str = str.replace(/abc/g, '');
When complete, you will still have 'test abc'!
The simplest loop to solve this would be:
var str = 'test aabcbc';
while (str != str.replace(/abc/g, '')){
str.replace(/abc/g, '');
}
But that runs the replacement twice for each cycle. Perhaps (at risk of being voted down) that can be combined for a slightly more efficient but less readable form:
var str = 'test aabcbc';
while (str != (str = str.replace(/abc/g, ''))){}
// alert(str); alerts 'test '!
This can be particularly useful when looking for duplicate strings.
For example, if we have 'a,,,b' and we wish to remove all duplicate commas.
[In that case, one could do .replace(/,+/g,','), but at some point the regex gets complex and slow enough to loop instead.]

How to use Javascript to change link [duplicate]

I've got a data-123 string.
How can I remove data- from the string while leaving the 123?

var ret = "data-123".replace('data-','');
console.log(ret); //prints: 123
Docs.
For all occurrences to be discarded use:
var ret = "data-123".replace(/data-/g,'');
PS: The replace function returns a new string and leaves the original string unchanged, so use the function return value after the replace() call.

This doesn't have anything to do with jQuery. You can use the JavaScript replace function for this:
var str = "data-123";
str = str.replace("data-", "");
You can also pass a regex to this function. In the following example, it would replace everything except numerics:
str = str.replace(/[^0-9\.]+/g, "");

You can use "data-123".replace('data-','');, as mentioned, but as replace() only replaces the FIRST instance of the matching text, if your string was something like "data-123data-" then
"data-123data-".replace('data-','');
will only replace the first matching text. And your output will be "123data-"
DEMO
So if you want all matches of text to be replaced in string you have to use a regular expression with the g flag like that:
"data-123data-".replace(/data-/g,'');
And your output will be "123"
DEMO2

You can use slice(), if you will know in advance how many characters need slicing off the original string. It returns characters between a given start point to an end point.
string.slice(start, end);
Here are some examples showing how it works:
var mystr = ("data-123").slice(5); // This just defines a start point so the output is "123"
var mystr = ("data-123").slice(5,7); // This defines a start and an end so the output is "12"
Demo

Plain old JavaScript will suffice - jQuery is not necessary for such a simple task:
var myString = "data-123";
var myNewString = myString.replace("data-", "");
See: .replace() docs on MDN for additional information and usage.

1- If is the sequences into your string:
let myString = "mytest-text";
let myNewString = myString.replace("mytest-", "");
the answer is text
2- if you whant to remove the first 3 characters:
"mytest-text".substring(3);
the answer is est-text

Ex:-
var value="Data-123";
var removeData=value.replace("Data-","");
alert(removeData);
Hopefully this will work for you.

Performance
Today 2021.01.14 I perform tests on MacOs HighSierra 10.13.6 on Chrome v87, Safari v13.1.2 and Firefox v84 for chosen solutions.
Results
For all browsers
solutions Ba, Cb, and Db are fast/fastest for long strings
solutions Ca, Da are fast/fastest for short strings
solutions Ab and E are slow for long strings
solutions Ba, Bb and F are slow for short strings
Details
I perform 2 tests cases:
short string - 10 chars - you can run it HERE
long string - 1 000 000 chars - you can run it HERE
Below snippet presents solutions
Aa
Ab
Ba
Bb
Ca
Cb
Da
Db
E
F
// https://stackoverflow.com/questions/10398931/how-to-strToRemove-text-from-a-string
// https://stackoverflow.com/a/10398941/860099
function Aa(str,strToRemove) {
return str.replace(strToRemove,'');
}
// https://stackoverflow.com/a/63362111/860099
function Ab(str,strToRemove) {
return str.replaceAll(strToRemove,'');
}
// https://stackoverflow.com/a/23539019/860099
function Ba(str,strToRemove) {
let re = strToRemove.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // regexp escape char
return str.replace(new RegExp(re),'');
}
// https://stackoverflow.com/a/63362111/860099
function Bb(str,strToRemove) {
let re = strToRemove.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // regexp escape char
return str.replaceAll(new RegExp(re,'g'),'');
}
// https://stackoverflow.com/a/27098801/860099
function Ca(str,strToRemove) {
let start = str.indexOf(strToRemove);
return str.slice(0,start) + str.slice(start+strToRemove.length, str.length);
}
// https://stackoverflow.com/a/27098801/860099
function Cb(str,strToRemove) {
let start = str.search(strToRemove);
return str.slice(0,start) + str.slice(start+strToRemove.length, str.length);
}
// https://stackoverflow.com/a/23181792/860099
function Da(str,strToRemove) {
let start = str.indexOf(strToRemove);
return str.substr(0, start) + str.substr(start + strToRemove.length);
}
// https://stackoverflow.com/a/23181792/860099
function Db(str,strToRemove) {
let start = str.search(strToRemove);
return str.substr(0, start) + str.substr(start + strToRemove.length);
}
// https://stackoverflow.com/a/49857431/860099
function E(str,strToRemove) {
return str.split(strToRemove).join('');
}
// https://stackoverflow.com/a/45406624/860099
function F(str,strToRemove) {
var n = str.search(strToRemove);
while (str.search(strToRemove) > -1) {
n = str.search(strToRemove);
str = str.substring(0, n) + str.substring(n + strToRemove.length, str.length);
}
return str;
}
let str = "data-123";
let strToRemove = "data-";
[Aa,Ab,Ba,Bb,Ca,Cb,Da,Db,E,F].map( f=> console.log(`${f.name.padEnd(2,' ')} ${f(str,strToRemove)}`));
This shippet only presents functions used in performance tests - it not perform tests itself!
And here are example results for chrome

This little function I made has always worked for me :)
String.prototype.deleteWord = function (searchTerm) {
var str = this;
var n = str.search(searchTerm);
while (str.search(searchTerm) > -1) {
n = str.search(searchTerm);
str = str.substring(0, n) + str.substring(n + searchTerm.length, str.length);
}
return str;
}
// Use it like this:
var string = "text is the cool!!";
string.deleteWord('the'); // Returns text is cool!!
I know it is not the best, but It has always worked for me :)

str.split('Yes').join('No');
This will replace all the occurrences of that specific string from original string.

I was used to the C# (Sharp) String.Remove method.
In Javascript, there is no remove function for string, but there is substr function.
You can use the substr function once or twice to remove characters from string.
You can make the following function to remove characters at start index to the end of string, just like the c# method first overload String.Remove(int startIndex):
function Remove(str, startIndex) {
return str.substr(0, startIndex);
}
and/or you also can make the following function to remove characters at start index and count, just like the c# method second overload String.Remove(int startIndex, int count):
function Remove(str, startIndex, count) {
return str.substr(0, startIndex) + str.substr(startIndex + count);
}
and then you can use these two functions or one of them for your needs!
Example:
alert(Remove("data-123", 0, 5));
Output: 123

Using match() and Number() to return a number variable:
Number(("data-123").match(/\d+$/));
// strNum = 123
Here's what the statement above does...working middle-out:
str.match(/\d+$/) - returns an array containing matches to any length of numbers at the end of str. In this case it returns an array containing a single string item ['123'].
Number() - converts it to a number type. Because the array returned from .match() contains a single element Number() will return the number.

Update 2023
There are many ways to solve this problem, but I believe this is the simplest:
const newString = string.split("data-").pop();
console.log(newString); /// 123

For doing such a thing there are a lot of different ways. A further way could be the following:
let str = 'data-123';
str = str.split('-')[1];
console.log('The remaining string is:\n' + str);
Basically the above code splits the string at the '-' char into two array elements and gets the second one, that is the one with the index 1, ignoring the first array element at the 0 index.
The following is one liner version:
console.log('The remaining string is:\n' + 'data-123'.split('-')[1]);
Another possible approach would be to add a method to the String prototype as follows:
String.prototype.remove = function (s){return this.replace(s,'')}
// After that it will be used like this:
a = 'ktkhkiksk kiksk ktkhkek kcklkekaknk kmkekskskakgkekk';
a = a.remove('k');
console.log(a);
Notice the above snippet will allow to remove only the first instance of the string you are interested to remove. But you can improve it a bit as follows:
String.prototype.removeAll = function (s){return this.replaceAll(s,'')}
// After that it will be used like this:
a = 'ktkhkiksk kiksk ktkhkek kcklkekaknk kmkekskskakgkekk';
a = a.removeAll('k');
console.log(a);
The above snippet instead will remove all instances of the string passed to the method.
Of course you don't need to implement the functions into the prototype of the String object: you can implement them as simple functions too if you wish (I will show the remove all function, for the other you will need to use just replace instead of replaceAll, so it is trivial to implement):
function strRemoveAll(s,r)
{
return s.replaceAll(r,'');
}
// you can use it as:
let a = 'ktkhkiksk kiksk ktkhkek kcklkekaknk kmkekskskakgkekk'
b = strRemoveAll (a,'k');
console.log(b);
Of course much more is possible.

Another way to replace all instances of a string is to use the new (as of August 2020) String.prototype.replaceAll() method.
It accepts either a string or RegEx as its first argument, and replaces all matches found with its second parameter, either a string or a function to generate the string.
As far as support goes, at time of writing, this method has adoption in current versions of all major desktop browsers* (even Opera!), except IE. For mobile, iOS SafariiOS 13.7+, Android Chromev85+, and Android Firefoxv79+ are all supported as well.
* This includes Edge/ Chrome v85+, Firefox v77+, Safari 13.1+, and Opera v71+
It'll take time for users to update to supported browser versions, but now that there's wide browser support, time is the only obstacle.
References:
MDN
Can I Use - Current Browser Support Information
TC39 Proposal Repo for .replaceAll()
You can test your current browser in the snippet below:
//Example coutesy of MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replaceAll
const p = 'The quick brown fox jumps over the lazy dog. If the dog reacted, was it really lazy?';
const regex = /dog/gi;
try {
console.log(p.replaceAll(regex, 'ferret'));
// expected output: "The quick brown fox jumps over the lazy ferret. If the ferret reacted, was it really lazy?"
console.log(p.replaceAll('dog', 'monkey'));
// expected output: "The quick brown fox jumps over the lazy monkey. If the monkey reacted, was it really lazy?"
console.log('Your browser is supported!');
} catch (e) {
console.log('Your browser is unsupported! :(');
}
.as-console-wrapper: {
max-height: 100% !important;
}

Make sure that if you are replacing strings in a loop that you initiate a new Regex in each iteration. As of 9/21/21, this is still a known issue with Regex essentially missing every other match. This threw me for a loop when I encountered this the first time:
yourArray.forEach((string) => {
string.replace(new RegExp(__your_regex__), '___desired_replacement_value___');
})
If you try and do it like so, don't be surprised if only every other one works
let reg = new RegExp('your regex');
yourArray.forEach((string) => {
string.replace(reg, '___desired_replacement_value___');
})

Javascript Regular Expressions - how to NOT match a substring between < and >

I'm using this regular expression:
var regex = /\<.*?.\>/g
to match with this string:
var str = 'This <is> a string to <use> to test the <regular> expression'
using a simple match:
str.match(regex)
and, as expected, I get:
["<is>", "<use>", "<regular>"]
(But without the backslashes, sorry for any potential confusion)
How can I get the reverse result? i.e. what regular expression do I need that does not return those items contained between < and >?
I tried /(^\<.*?\>)/g and various other similar combos including square brackets and stuff. I've got loads of cool results, just nothing that is quite what I want.
Where I'm going with this: Basically I want to search and replace occurences of substrings but I want to exclude some of the search space, probably using < and >. I don't really want a destructive method as I don't want to break apart strings, change them, and worry about reconstructing them.
Of course I could do this 'manually' by searching through the string but I figured regular expressions should be able to handle this rather well. Alas, my knowledge is not where it needs to be!!

Here's a way to do custom replacement of everything outside of the tags, and to strip the tags from the tagged parts http://jsfiddle.net/tcATT/
var string = 'This <is> a string to <use> to test the <regular> expression';
// The regular expression matches everything, but each val is either a
// tagged value (<is> <regular>), or the text you actually want to replace
// you need to decide that in the replacer function
console.log(str.replace( /[^<>]+|<.*?>/g, function(val){
if(val.charAt(0) == '<' && val.charAt(val.length - 1) == '>') {
// Just strip the < and > from the ends
return val.slice(1,-1);
} else {
// Do whatever you want with val here, I'm upcasing for simplicity
return val.toUpperCase();
}
} ));​
// outputs: "THIS is A STRING TO use TO TEST THE regular EXPRESSION"
To generalize it, you could use
function replaceOutsideTags(str, replacer) {
return str.replace( /[^<>]+|<.*?>/g, function(val){
if(val.charAt(0) == '<' && val.charAt(val.length - 1) == '>') {
// Just strip the < and > from the ends
return val.slice(1,-1);
} else {
// Let the caller decide how to replace the parts that need replacing
return replacer(val);
}
})
}
// And call it like
console.log(
replaceOutsideTags( str, function(val){
return val.toUpperCase();
})
);

If I understand correctly you want to apply some custom processing to a string except parts that are protected (enclosed in with < and >)? If, this is the case you could do it like this:
// The function that processes unprotected parts
function process(s) {
// an example could be transforming whole part to uppercase:
return s.toUpperCase();
}
// The function that splits string into chunks and applies processing
// to unprotected parts
function applyProcessing (s) {
var a = s.split(/<|>/),
out = '';
for (var i=0; i<a.length; i++)
out += i%2
? a[i]
: process(a[i]);
return out;
}
// now we just call the applyProcessing()
var str1 = 'This <is> a string to <use> to test the <regular> expression';
console.log(applyProcessing(str1));
// This outputs:
// "THIS is A STRING TO use TO TEST THE regular EXPRESSION"
// and another string:
var str2 = '<do not process this part!> The <rest> of the a <string>.';
console.log(applyProcessing(str2));
// This outputs:
// "do not process this part! THE rest OF THE A string."
This is basically it. It returns the whole string with the unprotected parts processed.
Please note that the splitting will not work correctly if the angle brackets (< and >) are not balanced.
There are various places that could be improved but I'll leave that as an excersize to the reader. ;p

This is a perfect application for passing a regex argument to the core String.split() method:
var results = str.split(/<[^<>]*>/);
Simple!

Using the variables you've already created, try using replace. It's non-destructive, too.
str.replace(regex, '');
--> "This a string to to test the expression"

/\b[^<\W]\w*(?!>)\b/g
This works, test it out:
var str = 'This <is> a string to <use> to test the <regular> expression.';
var regex = /\<.*?.>/g;
console.dir(str.match(regex));
var regex2 = /\b[^<\W]\w*(?!>)\b/g;
console.dir(str.match(regex2));

Ah, okay, sorry - I misunderstood your question. This is a difficult problem to solve with pure regular expressions in javascript, because javascript doesn't support lookbehinds, and usually I think I would use lookaheads and lookbehinds to solve this. A (sort of contrived) way of doing it would be something like this:
str.replace(/((?:<[^>]+>)?)([^<]*)/g, function (m, sep, s) { return sep + s.replace('test', 'FOO'); })
// --> "This <is> a string to <use> to FOO the <regular> expression"
This also works on strings like "This test <is> a string to <use> to test the <regular> expression", and if you use /test/g instead of 'test' in the replacer function, it will also turn
"This test <is> a string to <use> to test the test <regular> expression"
into
"This FOO <is> a string to <use> to FOO the FOO <regular> expression"
UPDATE
And something like this would also strip the <> characters:
str.replace(/((?:<[^>]+>)?)([^<]*)/g, function (m, sep, s) { return sep.replace(/[<>]/g, '') + s.replace(/test/g, 'FOO'); })
"This test <is> a string to <use> to test the test <regular> expression"
--> "This FOO is a string to use to FOO the FOO regular expression"

Try this regex:
\b\w+\b(?!>)
UPDATE
To support spaces inside brackets try this one. It's not pure regex.match, but it works and it's much simpler that the answer above:
alert('This <is> a string to <use use> to test the <regular> expression'.split(/\s*<.+?>\s*/).join(' '));

Replacing multiple patterns in a block of data

I need to find the most efficient way of matching multiple regular expressions on a single block of text. To give an example of what I need, consider a block of text:
"Hello World what a beautiful day"
I want to replace Hello with "Bye" and "World" with Universe. I can always do this in a loop ofcourse, using something like String.replace functions availiable in various languages.
However, I could have a huge block of text with multiple string patterns, that I need to match and replace.
I was wondering if I can use Regular Expressions to do this efficiently or do I have to use a Parser like LALR.
I need to do this in JavaScript, so if anyone knows tools that can get it done, it would be appreciated.

Edit
6 years after my original answer (below) I would solve this problem differently
function mreplace (replacements, str) {
let result = str;
for (let [x, y] of replacements)
result = result.replace(x, y);
return result;
}
let input = 'Hello World what a beautiful day';
let output = mreplace ([
[/Hello/, 'Bye'],
[/World/, 'Universe']
], input);
console.log(output);
// "Bye Universe what a beautiful day"
This has as tremendous advantage over the previous answer which required you to write each match twice. It also gives you individual control over each match. For example:
function mreplace (replacements, str) {
let result = str;
for (let [x, y] of replacements)
result = result.replace(x, y);
return result;
}
let input = 'Hello World what a beautiful day';
let output = mreplace ([
//replace static strings
['day', 'night'],
// use regexp and flags where you want them: replace all vowels with nothing
[/[aeiou]/g, ''],
// use captures and callbacks! replace first capital letter with lowercase
[/([A-Z])/, $0 => $0.toLowerCase()]
], input);
console.log(output);
// "hll Wrld wht btfl nght"
Original answer
Andy E's answer can be modified to make adding replacement definitions easier.
var text = "Hello World what a beautiful day";
text.replace(/(Hello|World)/g, function ($0){
var index = {
'Hello': 'Bye',
'World': 'Universe'
};
return index[$0] != undefined ? index[$0] : $0;
});
// "Bye Universe what a beautiful day";

You can pass a function to replace:
var hello = "Hello World what a beautiful day";
hello.replace(/Hello|World/g, function ($0, $1, $2) // $3, $4... $n for captures
{
if ($0 == "Hello")
return "Bye";
else if ($0 == "World")
return "Universe";
});
// Output: "Bye Universe what a beautiful day";

An improved answer:
var index = {
'Hello': 'Bye',
'World': 'Universe'
};
var pattern = '';
for (var i in index) {
if (pattern != '') pattern += '|';
pattern += i;
}
var text = "Hello World what a beautiful day";
text.replace(new RegExp(pattern, 'g'), function($0) {
return index[$0] != undefined ? index[$0] : $0;
});

If the question is how to replace multiple generic patterns with corresponding replacements - either strings or functions, it's quite tricky because of special characters, capturing groups and backreference matching.
You can use https://www.npmjs.com/package/union-replacer for this exact purpose. It is basically a string.replace(regexp, string|function) counterpart, which allows multiple replaces to happen in one pass while preserving full power of string.replace(...).
Disclosure: I am the author and the library was developed because we had to support user-configured replaces.

A common task involving replacing a number of patterns is making a user's or other string "safe" for rendering on Web pages, which means preventing HTML tags from being active. This can be done in JavaScript using HTML entities and the forEach function, allowing a set of exceptions (that is, a set of HTML tags that will be allowed to render).
This is a common task, and here is a fairly brief way to accomplish it:
// Make a string safe for rendering or storing on a Web page
function SafeHTML(str)
{
// Make all HTML tags safe
let s=str.replace(/</gi,'<');
// Allow certain safe tags to be rendered
['br','strong'].forEach(item=>
{
let p=new RegExp('<(/?)'+item+'>','gi');
s=s.replace(p,'<$1'+item+'>');
});
return s;
} // SafeHTML

Case insensitive string replacement in JavaScript?

I need to highlight, case insensitively, given keywords in a JavaScript string.
For example:
highlight("foobar Foo bar FOO", "foo") should return "<b>foo</b>bar <b>Foo</b> bar <b>FOO</b>"
I need the code to work for any keyword, and therefore using a hardcoded regular expression like /foo/i is not a sufficient solution.
What is the easiest way to do this?
(This an instance of a more general problem detailed in the title, but I feel that it's best to tackle with a concrete, useful example.)

You can use regular expressions if you prepare the search string. In PHP e.g. there is a function preg_quote, which replaces all regex-chars in a string with their escaped versions.
Here is such a function for javascript (source):
function preg_quote (str, delimiter) {
// discuss at: https://locutus.io/php/preg_quote/
// original by: booeyOH
// improved by: Ates Goral (https://magnetiq.com)
// improved by: Kevin van Zonneveld (https://kvz.io)
// improved by: Brett Zamir (https://brett-zamir.me)
// bugfixed by: Onno Marsman (https://twitter.com/onnomarsman)
// example 1: preg_quote("$40")
// returns 1: '\\$40'
// example 2: preg_quote("*RRRING* Hello?")
// returns 2: '\\*RRRING\\* Hello\\?'
// example 3: preg_quote("\\.+*?[^]$(){}=!<>|:")
// returns 3: '\\\\\\.\\+\\*\\?\\[\\^\\]\\$\\(\\)\\{\\}\\=\\!\\<\\>\\|\\:'
return (str + '')
.replace(new RegExp('[.\\\\+*?\\[\\^\\]$(){}=!<>|:\\' + (delimiter || '') + '-]', 'g'), '\\$&')
}
So you could do the following:
function highlight(str, search) {
return str.replace(new RegExp("(" + preg_quote(search) + ")", 'gi'), "<b>$1</b>");
}

function highlightWords( line, word )
{
var regex = new RegExp( '(' + word + ')', 'gi' );
return line.replace( regex, "<b>$1</b>" );
}

You can enhance the RegExp object with a function that does special character escaping for you:
RegExp.escape = function(str)
{
var specials = /[.*+?|()\[\]{}\\$^]/g; // .*+?|()[]{}\$^
return str.replace(specials, "\\$&");
}
Then you would be able to use what the others suggested without any worries:
function highlightWordsNoCase(line, word)
{
var regex = new RegExp("(" + RegExp.escape(word) + ")", "gi");
return line.replace(regex, "<b>$1</b>");
}

Regular expressions are fine as long as keywords are really words, you can just use a RegExp constructor instead of a literal to create one from a variable:
var re= new RegExp('('+word+')', 'gi');
return s.replace(re, '<b>$1</b>');
The difficulty arises if ‘keywords’ can have punctuation in, as punctuation tends to have special meaning in regexps. Unfortunately unlike most other languages/libraries with regexp support, there is no standard function to escape punctation for regexps in JavaScript.
And you can't be totally sure exactly what characters need escaping because not every browser's implementation of regexp is guaranteed to be exactly the same. (In particular, newer browsers may add new functionality.) And backslash-escaping characters that are not special is not guaranteed to still work, although in practice it does.
So about the best you can do is one of:
attempting to catch each special character in common browser use today [add: see Sebastian's recipe]
backslash-escape all non-alphanumerics. care: \W will also match non-ASCII Unicode characters, which you don't really want.
just ensure that there are no non-alphanumerics in the keyword before searching
If you are using this to highlight words in HTML which already has markup in, though, you've got trouble. Your ‘word’ might appear in an element name or attribute value, in which case attempting to wrap a < b> around it will cause brokenness. In more complicated scenarios possibly even an HTML-injection to XSS security hole. If you have to cope with markup you will need a more complicated approach, splitting out ‘< ... >’ markup before attempting to process each stretch of text on its own.

What about something like this:
if(typeof String.prototype.highlight !== 'function') {
String.prototype.highlight = function(match, spanClass) {
var pattern = new RegExp( match, "gi" );
replacement = "<span class='" + spanClass + "'>$&</span>";
return this.replace(pattern, replacement);
}
}
This could then be called like so:
var result = "The Quick Brown Fox Jumped Over The Lazy Brown Dog".highlight("brown","text-highlight");

For those poor with disregexia or regexophobia:
function replacei(str, sub, f){
let A = str.toLowerCase().split(sub.toLowerCase());
let B = [];
let x = 0;
for (let i = 0; i < A.length; i++) {
let n = A[i].length;
B.push(str.substr(x, n));
if (i < A.length-1)
B.push(f(str.substr(x + n, sub.length)));
x += n + sub.length;
}
return B.join('');
}
s = 'Foo and FOO (and foo) are all -- Foo.'
t = replacei(s, 'Foo', sub=>'<'+sub+'>')
console.log(t)
Output:
<Foo> and <FOO> (and <foo>) are all -- <Foo>.

Why not just create a new regex on each call to your function? You can use:
new Regex([pat], [flags])
where [pat] is a string for the pattern, and [flags] are the flags.