Keep only one occurrence of substring in a string - javascript

I'm looking for a function that removes all occurrences of a substring in a string except the first one, so for example
function keepFirst(str, substr) { ... }
keepFirst("This $ is some text $.", "$");
should return: This $ is some text .
I could do it using split() and then for(){}, but is there a nicer solution?

This could be the shortest code that is somewhat efficient. It uses destructuring assignment.
function keepFirst(str, substr) {
const [
first,
...rest
] = str.split(substr);
return first + (rest.length
? substr + rest.join("")
: "");
}

This solution finds the index of the first occurence of rep and removes all of the reps after it.
console.log(keepFirst("This $ is some text $$ with $ signs.", "$"));
function keepFirst(str, rep) {
var fInd = str.indexOf(rep);
var first = str.substring(0, fInd + rep.length);
var rest = str.substring(fInd + rep.length);
return first + rest.replace(
new RegExp(rep.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"), 'g'),
'');
}

Related

RegExp replace all letter but not first and last

I have to replace all letters of name on ****.
Example:
Jeniffer -> J****r
I try $(this).text( $(this).text().replace(/([^\w])\//g, "*"))
Also, if name is Ron -> R****n
You can use a regular expression for this, by capturing the first and last letters in a capture group and ignoring all letters between them, then using the capture groups in the replacement:
var updated = name.replace(/^(.).*(.)$/, "$1****$2");
Live Example:
function obscure(name) {
return name.replace(/^(.).*(.)$/, "$1****$2");
}
function test(name) {
console.log(name, "=>", obscure(name));
}
test("Ron");
test("Jeniffer");
But it's perhaps easier without:
var updated = name[0] + "****" + name[name.length - 1];
Live Example:
function obscure(name) {
return name[0] + "****" + name[name.length - 1];;
}
function test(name) {
console.log(name, "=>", obscure(name));
}
test("Ron");
test("Jeniffer");
Both of those do assume the names will be at least two characters long. I pity the fool who tries this on Mr. T's surname.
Since, you need to have four asterisk on each condition, you can create a reusable function that will create this format for you:
function replace(str){
var firstChar = str.charAt(0);
var lastChar = str.charAt(str.length-1);
return firstChar + '****' + lastChar;
}
var str = 'Jeniffer';
console.log(replace(str));
str = 'America';
console.log(replace(str))
Appears that you're looking for regex lookaround
Regex: (?<=\w)(\w+)(?=\w) - group 1 matches all characters which follow one character and followed by another one.
Tests: https://regex101.com/r/PPeEqx/2/
More Info: https://www.regular-expressions.info/lookaround.html
Find first and last chars and append **** to the first one and add the last one:
const firstName = 'Jeniffer';
const result = firstName.match(/^.|.$/gi).reduce((s, c, i) => `${s}${!i ? `${c}****` : c }`, '');
console.log(result);

Capitalize first letter of each word in JS

I'm learning how to capitalize the first letter of each word in a string and for this solution I understand everything except the word.substr(1) portion. I see that it's adding the broken string but how does the (1) work?
function toUpper(str) {
return str
.toLowerCase()
.split(' ')
.map(function(word) {
return word[0].toUpperCase() + word.substr(1);
})
.join(' ');
}
console.log(toUpper("hello friend"))
The return value contain 2 parts:
return word[0].toUpperCase() + word.substr(1);
1) word[0].toUpperCase(): It's the first capital letter
2) word.substr(1) the whole remain word except the first letter which has been capitalized. This is document for how substr works.
Refer below result if you want to debug:
function toUpper(str) {
return str
.toLowerCase()
.split(' ')
.map(function(word) {
console.log("First capital letter: "+word[0]);
console.log("remain letters: "+ word.substr(1));
return word[0].toUpperCase() + word.substr(1);
})
.join(' ');
}
console.log(toUpper("hello friend"))
Or you could save a lot of time and use Lodash
Look at
https://lodash.com/docs/4.17.4#startCase -added/edited-
https://lodash.com/docs/4.17.4#capitalize
Ex.
-added/edited-
You may what to use startCase, another function for capitalizing first letter of each word.
_.startCase('foo bar');
// => 'Foo Bar'
and capitalize for only the first letter on the sentence
_.capitalize('FRED');
// => 'Fred'
Lodash is a beautiful js library made to save you a lot of time.
There you will find a lot of time saver functions for strings, numbers, arrays, collections, etc.
Also you can use it on client or server (nodejs) side, use bower or node, cdn or include it manually.
Here is a quick code snippet. This code snippet will allow you to capitalize the first letter of a string using JavaScript.
function capitlizeText(word)
{
return word.charAt(0).toUpperCase() + word.slice(1);
}
The regexp /\b\w/ matches a word boundary followed by a word character. You can use this with the replace() string method to match then replace such characters (without the g (global) regexp flag only the first matching char is replaced):
> 'hello my name is ...'.replace(/\b\w/, (c) => c.toUpperCase());
'Hello my name is ...'
> 'hello my name is ...'.replace(/\b\w/g, (c) => c.toUpperCase());
'Hello My Name Is ...'
function titleCase(str) {
return str.toLowerCase().split(' ').map(x=>x[0].toUpperCase()+x.slice(1)).join(' ');
}
titleCase("I'm a little tea pot");
titleCase("sHoRt AnD sToUt");
The major part of the answers explains to you how works the substr(1). I give to you a better aproach to resolve your problem
function capitalizeFirstLetters(str){
return str.toLowerCase().replace(/^\w|\s\w/g, function (letter) {
return letter.toUpperCase();
})
}
Explanation:
- First convert the entire string to lower case
- Second check the first letter of the entire string and check the first letter that have a space character before and replaces it applying .toUpperCase() method.
Check this example:
function capitalizeFirstLetters(str){
return str.toLowerCase().replace(/^\w|\s\w/g, function (letter) {
return letter.toUpperCase();
})
}
console.log(capitalizeFirstLetters("a lOt of words separated even much spaces "))
Consider an arrow function with an implicit return:
word => `${word.charAt(0).toUpperCase()}${word.slice(1).toLowerCase()}`
This will do it in one line.
Using ES6
let captalizeWord = text => text.toLowerCase().split(' ').map( (i, j) => i.charAt(0).toUpperCase()+i.slice(1)).join(' ')
captalizeWord('cool and cool')
substr is a function that returns (from the linked MDN) a new string containing the extracted section of the given string (starting from the second character in your function). There is a comment on the polyfill implementation as well, which adds Get the substring of a string.
function titlecase(str){
let titlecasesentence = str.split(' ');
titlecasesentence = titlecasesentence.map((word)=>{
const firstletter = word.charAt(0).toUpperCase();
word = firstletter.concat(word.slice(1,word.length));
return word;
});
titlecasesentence = titlecasesentence.join(' ');
return titlecasesentence;
}
titlecase('this is how to capitalize the first letter of a word');
const capitalize = str => {
if (typeof str !== 'string') {
throw new Error('Invalid input: input must of type "string"');
}
return str
.trim()
.replace(/ {1,}/g, ' ')
.toLowerCase()
.split(' ')
.map(word => word[0].toUpperCase() + word.slice(1))
.join(' ');
};
sanitize the input string with trim() to remove whitespace from the leading and trailing ends
replace any extra spaces in the middle with a RegExp
normalize and convert it all toLowerCase() letters
convert the string to an array split on spaces
map that array into an array of capitalized words
join(' ') the array with spaces and return the newly capitalized string
Whole sentence will be capitalize only by one line
"my name is John".split(/ /g).map(val => val[0].toUpperCase() + val.slice(1)).join(' ')
Output "My Name Is John"
A nice simple solution, using pure JavaScript. JSFiddle
function initCap(s) {
var result = '';
if ((typeof (s) === 'undefined') || (s == null)) {
return result;
}
s = s.toLowerCase();
var words = s.split(' ');
for (var i = 0; i < words.length; ++i) {
result += (i > 0 ? ' ' : '') +
words[i].substring(0, 1).toUpperCase() +
words[i].substring(1);
}
return result;
}
Here is an example of how substr works: When you pass in a number, it takes a portion of the string based on the index you provided:
console.log('Testing string'.substr(0)); // Nothing different
console.log('Testing string'.substr(1)); // Starts from index 1 (position 2)
console.log('Testing string'.substr(2));
So, they are taking the first letter of each word, capitalizing it, and then adding on the remaining of the word. Ance since you are only capitalizing the first letter, the index to start from is always 1.
In word.substr(i), the param means the index of the word. This method cuts the word from the letter whose index equals i to the end of the word.
You can also add another param like word.substr(i, len), where len means the length of the character segmentation. For example:
'abcde'.substr(1, 2) → bc.
function toTitleCase(str)
{
return str.replace(/\w\S*/g, function(txt){return
txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase();});
}
Just map through if an array set the first letter as uppercase and concatenate with other letters from index 1.
The array isn't your case here.
const capitalizeNames = (arr) => {
arr.map((name) => {
let upper = name[0].toUpperCase() + name.substr(1)
console.log(upper)
})
}
Here's another clean way of Capitalizing sentences/names/... :
const capitalizeNames =(name)=>{
const names = name.split(' ') // ['kouhadi','aboubakr',essaaddik']
const newCapName = [] // declaring an empty array
for (const n of names){
newCapName.push(n.replace(n[0], n[0].toUpperCase()));
}
return newCapName.join(' ')
}
capitalizeNames('kouhadi aboubakr essaaddik'); // 'Kouhadi Aboubakr Essaaddik'
You could use these lines of code:
function toUpper(str) {
return [str.split('')[0].toUpperCase(), str.split('').slice(1, str.split('').length).join("")].join("")
}
Basically it will split all characters, slice it, create a new array without the first entry/character and replace the first entry/character with an uppercase verion of the character.
(Yes, this was tested and it works on Edge, Chrome and newer versions of Internet Explorer.)
This is probably not the greatest answer, but hopefully it works well enough for you.

Replace string between second set of [ and ]

I am learning regex, and I got a doubt. Let's consider
var s = "YYYN[1-20]N[]NYY";
Now, I want to replace/insert the '1-8' between [ and ] at its second occurrence.
Then output should be
YYYN[1-20]N[1-8]NYY
For that I had tried using replace and passing a function through it as shown below:
var nth = 0;
s = s.replace(/\[([^)]+)\]/g, function(match, i, original) {
nth++;
return (nth === 1) ? "1-8" : match;
});
alert(s); // But It wont work
I think that regex is not matchIing the string that I am using.
How can I fix it?
You regex \[([^)]+)\] will not match empty square brackets since + requires at least 1 character other than ). I guess you wanted to write \[[^\]]*\].
Here is a fix for your solution:
var s = "YYYN[1-20]N[]NYY";
var nth = 0;
s = s.replace(/\[[^\]]*\]/g, function (match, i, original) {
nth++;
return (nth !== 1) ? "[1-8]" : match;
});
alert(s);
Here is another way of doing it:
var s = "YYYN[1-20]N[]NYY";
var nth = 0;
s = s.replace(/(.*)\[\]/, "$1[1-8]");
alert(s);
The regex (.*)\[\] matches and captures into Group 1 greedily as much text as possible (thus we get the last set of empty []), and then matches empty square brackets. Then we restore the text before [] with $1 backreference and add out string 1-8.
If it’s only two occurences of square brackets, then this will work:
/(.*\[.*?\].*\[).*?(\].*)/
This RegEx has “YYYN[1-20]N[” as the first capturing group and “]NYY” as the second.
I suggest using simple split and join operations:
var s = "YYYN[1-20]N[]NYY";
var arr = s.split(/\[/)
arr[2] = '1-8' + arr[2]
var r = arr.join('[')
//=> YYYN[1-20]N[1-8]NYY
You can use following regex :
var s = "YYYN[1-20]N[]NYY";
var nth = 0;
s = s.replace(/([^[]+\[(?:[^[]+)\][^[]+)\[[^[]+\](.+)/, "$1[1-8]$2");
alert(s);
The first part ([^[]+\[([^[]+)\][^[]+) will match a string contain first sub-string between []. and \[[^[]+\] would be the second one which you want and the last part (.+?) match the rest of your string.

Replace substring in string with range in JavaScript

How can I replace a substring of a string given the starting position and the length?
I was hoping for something like this:
var string = "This is a test string";
string.replace(10, 4, "replacement");
so that string would equal
"this is a replacement string"
..but I can't find anything like that.
Any help appreciated.
Like this:
var outstr = instr.substr(0,start)+"replacement"+instr.substr(start+length);
You can add it to the string's prototype:
String.prototype.splice = function(start,length,replacement) {
return this.substr(0,start)+replacement+this.substr(start+length);
}
(I call this splice because it is very similar to the Array function of the same name)
For what it's worth, this function will replace based on two indices instead of first index and length.
splice: function(specimen, start, end, replacement) {
// string to modify, start index, end index, and what to replace that selection with
var head = specimen.substring(0,start);
var body = specimen.substring(start, end + 1); // +1 to include last character
var tail = specimen.substring(end + 1, specimen.length);
var result = head + replacement + tail;
return result;
}
Short RegExp version:
str.replace(new RegExp("^(.{" + start + "}).{" + length + "}"), "$1" + word);
Example:
String.prototype.sreplace = function(start, length, word) {
return this.replace(
new RegExp("^(.{" + start + "}).{" + length + "}"),
"$1" + word);
};
"This is a test string".sreplace(10, 4, "replacement");
// "This is a replacement string"
DEMO: http://jsfiddle.net/9zP7D/
The Underscore String library has a splice method which works exactly as you specified.
_("This is a test string").splice(10, 4, 'replacement');
=> "This is a replacement string"
There are a lot of other useful functions in the library as well. It clocks in at 8kb and is available on cdnjs.

How can I remove a character from a string using JavaScript?

I am so close to getting this, but it just isn't right.
All I would like to do is remove the character r from a string.
The problem is, there is more than one instance of r in the string.
However, it is always the character at index 4 (so the 5th character).
Example string: crt/r2002_2
What I want: crt/2002_2
This replace function removes both r
mystring.replace(/r/g, '')
Produces: ct/2002_2
I tried this function:
String.prototype.replaceAt = function (index, char) {
return this.substr(0, index) + char + this.substr(index + char.length);
}
mystring.replaceAt(4, '')
It only works if I replace it with another character. It will not simply remove it.
Any thoughts?
var mystring = "crt/r2002_2";
mystring = mystring.replace('/r','/');
will replace /r with / using String.prototype.replace.
Alternatively you could use regex with a global flag (as suggested by Erik Reppen & Sagar Gala, below) to replace all occurrences with
mystring = mystring.replace(/\/r/g, '/');
EDIT:
Since everyone's having so much fun here and user1293504 doesn't seem to be coming back any time soon to answer clarifying questions, here's a method to remove the Nth character from a string:
String.prototype.removeCharAt = function (i) {
var tmp = this.split(''); // convert to an array
tmp.splice(i - 1 , 1); // remove 1 element from the array (adjusting for non-zero-indexed counts)
return tmp.join(''); // reconstruct the string
}
console.log("crt/r2002_2".removeCharAt(4));
Since user1293504 used the normal count instead of a zero-indexed count, we've got to remove 1 from the index, if you wish to use this to replicate how charAt works do not subtract 1 from the index on the 3rd line and use tmp.splice(i, 1) instead.
A simple functional javascript way would be
mystring = mystring.split('/r').join('/')
simple, fast, it replace globally and no need for functions or prototypes
There's always the string functions, if you know you're always going to remove the fourth character:
str.slice(0, 4) + str.slice(5, str.length)
Your first func is almost right. Just remove the 'g' flag which stands for 'global' (edit) and give it some context to spot the second 'r'.
Edit: didn't see it was the second 'r' before so added the '/'. Needs \/ to escape the '/' when using a regEx arg. Thanks for the upvotes but I was wrong so I'll fix and add more detail for people interested in understanding the basics of regEx better but this would work:
mystring.replace(/\/r/, '/')
Now for the excessive explanation:
When reading/writing a regEx pattern think in terms of: <a character or set of charcters> followed by <a character or set of charcters> followed by <...
In regEx <a character or set of charcters> could be one at a time:
/each char in this pattern/
So read as e, followed by a, followed by c, etc...
Or a single <a character or set of charcters> could be characters described by a character class:
/[123!y]/
//any one of these
/[^123!y]/
//anything but one of the chars following '^' (very useful/performance enhancing btw)
Or expanded on to match a quantity of characters (but still best to think of as a single element in terms of the sequential pattern):
/a{2}/
//precisely two 'a' chars - matches identically as /aa/ would
/[aA]{1,3}/
//1-3 matches of 'a' or 'A'
/[a-zA-Z]+/
//one or more matches of any letter in the alphabet upper and lower
//'-' denotes a sequence in a character class
/[0-9]*/
//0 to any number of matches of any decimal character (/\d*/ would also work)
So smoosh a bunch together:
var rePattern = /[aA]{4,8}(Eat at Joes|Joes all you can eat)[0-5]+/g
var joesStr = 'aaaAAAaaEat at Joes123454321 or maybe aAaAJoes all you can eat098765';
joesStr.match(rePattern);
//returns ["aaaAAAaaEat at Joes123454321", "aAaAJoes all you can eat0"]
//without the 'g' after the closing '/' it would just stop at the first match and return:
//["aaaAAAaaEat at Joes123454321"]
And of course I've over-elaborated but my point was simply that this:
/cat/
is a series of 3 pattern elements (a thing followed by a thing followed by a thing).
And so is this:
/[aA]{4,8}(Eat at Joes|Joes all you can eat)[0-5]+/
As wacky as regEx starts to look, it all breaks down to series of things (potentially multi-character things) following each other sequentially. Kind of a basic point but one that took me a while to get past so I've gone overboard explaining it here as I think it's one that would help the OP and others new to regEx understand what's going on. The key to reading/writing regEx is breaking it down into those pieces.
Just fix your replaceAt:
String.prototype.replaceAt = function(index, charcount) {
return this.substr(0, index) + this.substr(index + charcount);
}
mystring.replaceAt(4, 1);
I'd call it removeAt instead. :)
For global replacement of '/r', this code worked for me.
mystring = mystring.replace(/\/r/g,'');
This is improvement of simpleigh answer (omit length)
s.slice(0, 4) + s.slice(5)
let s = "crt/r2002_2";
let o = s.slice(0, 4) + s.slice(5);
let delAtIdx = (s, i) => s.slice(0, i) + s.slice(i + 1); // this function remove letter at index i
console.log(o);
console.log(delAtIdx(s, 4));
let str = '1234567';
let index = 3;
str = str.substring(0, index) + str.substring(index + 1);
console.log(str) // 123567 - number "4" under index "3" is removed
return this.substr(0, index) + char + this.substr(index + char.length);
char.length is zero. You need to add 1 in this case in order to skip character.
Maybe I'm a noob, but I came across these today and they all seem unnecessarily complicated.
Here's a simpler (to me) approach to removing whatever you want from a string.
function removeForbiddenCharacters(input) {
let forbiddenChars = ['/', '?', '&','=','.','"']
for (let char of forbiddenChars){
input = input.split(char).join('');
}
return input
}
Create function like below
String.prototype.replaceAt = function (index, char) {
if(char=='') {
return this.slice(0,index)+this.substr(index+1 + char.length);
} else {
return this.substr(0, index) + char + this.substr(index + char.length);
}
}
To replace give character like below
var a="12346";
a.replaceAt(4,'5');
and to remove character at definite index, give second parameter as empty string
a.replaceAt(4,'');
If it is always the 4th char in yourString you can try:
yourString.replace(/^(.{4})(r)/, function($1, $2) { return $2; });
It only works if I replace it with another character. It will not simply remove it.
This is because when char is equal to "", char.length is 0, so your substrings combine to form the original string. Going with your code attempt, the following will work:
String.prototype.replaceAt = function (index, char) {
return this.substr(0, index) + char + this.substr(index + 1);
// this will 'replace' the character at index with char ^
}
DEMO
You can use this: if ( str[4] === 'r' ) str = str.slice(0, 4) + str.slice(5)
Explanation:
if ( str[4] === 'r' )
Check if the 5th character is a 'r'
str.slice(0, 4)
Slice the string to get everything before the 'r'
+ str.slice(5)
Add the rest of the string.
Minified: s=s[4]=='r'?s.slice(0,4)+s.slice(5):s [37 bytes!]
DEMO:
function remove5thR (s) {
s=s[4]=='r'?s.slice(0,4)+s.slice(5):s;
console.log(s); // log output
}
remove5thR('crt/r2002_2') // > 'crt/2002_2'
remove5thR('crt|r2002_2') // > 'crt|2002_2'
remove5thR('rrrrr') // > 'rrrr'
remove5thR('RRRRR') // > 'RRRRR' (no change)
If you just want to remove single character and
If you know index of a character you want to remove, you can use following function:
/**
* Remove single character at particular index from string
* #param {*} index index of character you want to remove
* #param {*} str string from which character should be removed
*/
function removeCharAtIndex(index, str) {
var maxIndex=index==0?0:index;
return str.substring(0, maxIndex) + str.substring(index, str.length)
}
I dislike using replace function to remove characters from string. This is not logical to do it like that. Usually I program in C# (Sharp), and whenever I want to remove characters from string, I use the Remove method of the String class, but no Replace method, even though it exists, because when I am about to remove, I remove, no replace. This is logical!
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("crt/r2002_2", 4, 1));
Output: crt/2002_2
Achieving goals by doing techniques with no logic might cause confusions in understanding of the code, and future mistakes, if you do this a lot in a large project!
The following function worked best for my case:
public static cut(value: string, cutStart: number, cutEnd: number): string {
return value.substring(0, cutStart) + value.substring(cutEnd + 1, value.length);
}
The shortest way would be to use splice
var inputString = "abc";
// convert to array and remove 1 element at position 4 and save directly to the array itself
let result = inputString.split("").splice(3, 1).join();
console.log(result);
This problem has many applications. Tweaking #simpleigh solution to make it more copy/paste friendly:
function removeAt( str1, idx) {
return str1.substr(0, idx) + str1.substr(idx+1)
}
console.log(removeAt('abbcdef', 1)) // prints: abcdef
Using [index] position for removing a specific char (s)
String.prototype.remplaceAt = function (index, distance) {
return this.slice(0, index) + this.slice(index + distance, this.length);
};
credit to https://stackoverflow.com/users/62576/ken-white
So basically, another way would be to:
Convert the string to an array using Array.from() method.
Loop through the array and delete all r letters except for the one with index 1.
Convert array back to a string.
let arr = Array.from("crt/r2002_2");
arr.forEach((letter, i) => { if(letter === 'r' && i !== 1) arr[i] = "" });
document.write(arr.join(""));
In C# (Sharp), you can make an empty character as '\0'.
Maybe you can do this:
String.prototype.replaceAt = function (index, char) {
return this.substr(0, index) + char + this.substr(index + char.length);
}
mystring.replaceAt(4, '\0')
Search on google or surf on the interent and check if javascript allows you to make empty characters, like C# does. If yes, then learn how to do it, and maybe the replaceAt function will work at last, and you'll achieve what you want!
Finally that 'r' character will be removed!

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