I need to display a formatted number on a web page using JavaScript. I want to format it so that there are commas in the right places. How would I do this with a regular expression? I've gotten as far as something like this:
myString = myString.replace(/^(\d{3})*$/g, "${1},");
...and then realized this would be more complex than I think (and the regex above is not even close to what I need). I've done some searching and I'm having a hard time finding something that works for this.
Basically, I want these results:
45 becomes 45
3856 becomes 3,856
398868483992 becomes 398,868,483,992
...you get the idea.
This can be done in a single regex, no iteration required. If your browser supports ECMAScript 2018, you could simply use lookaround and just insert commas at the right places:
Search for (?<=\d)(?=(\d\d\d)+(?!\d)) and replace all with ,
In older versions, JavaScript doesn't support lookbehind, so that doesn't work. Fortunately, we only need to change a little bit:
Search for (\d)(?=(\d\d\d)+(?!\d)) and replace all with \1,
So, in JavaScript, that would look like:
result = subject.replace(/(\d)(?=(\d\d\d)+(?!\d))/g, "$1,");
Explanation: Assert that from the current position in the string onwards, it is possible to match digits in multiples of three, and that there is a digit left of the current position.
This will also work with decimals (123456.78) as long as there aren't too many digits "to the right of the dot" (otherwise you get 123,456.789,012).
You can also define it in a Number prototype, as follows:
Number.prototype.format = function(){
return this.toString().replace(/(\d)(?=(\d{3})+(?!\d))/g, "$1,");
};
And then using it like this:
var num = 1234;
alert(num.format());
Credit: Jeffrey Friedl, Mastering Regular Expressions, 3rd. edition, p. 66-67
Formatting a number can be handled elegantly with one line of code.
This code extends the Number object; usage examples are included below.
Code:
Number.prototype.format = function () {
return this.toString().split( /(?=(?:\d{3})+(?:\.|$))/g ).join( "," );
};
How it works
The regular expression uses a look-ahead to find positions within the string where the only thing to the right of it is one or more groupings of three numbers, until either a decimal or the end of string is encountered. The .split() is used to break the string at those points into array elements, and then the .join() merges those elements back into a string, separated by commas.
The concept of finding positions within the string, rather than matching actual characters, is important in order to split the string without removing any characters.
Usage examples:
var n = 9817236578964235;
alert( n.format() ); // Displays "9,817,236,578,964,235"
n = 87345.87;
alert( n.format() ); // Displays "87,345.87"
Of course, the code can easily be extended or changed to handle locale considerations. For example, here is a new version of the code that automatically detects the locale settings and swaps the use of commas and periods.
Locale-aware version:
Number.prototype.format = function () {
if ((1.1).toLocaleString().indexOf(".") >= 0) {
return this.toString().split( /(?=(?:\d{3})+(?:\.|$))/g ).join( "," );
}
else {
return this.toString().split( /(?=(?:\d{3})+(?:,|$))/g ).join( "." );
}
};
Unless it's really necessary, I prefer the simplicity of the first version though.
With the caveat that Intl.NumberFormat and Number.toLocaleString() are now there for this purpose in JavaScript:
The other answers using regular expressions all break down for decimal numbers (although the authors seem to not know this because they have only tested with 1 or 2 decimal places). This is because without lookbehind, JS regular expressions have no way to know whether you are working with the block of digits before or after the decimal point. That leaves two ways to address this with JS regular expressions:
Know whether there is a decimal point in the number, and use different regular expressions depending on that:
/(\d)(?=(\d{3})+$)/g for integers
/(\d)(?=(\d{3})+\.)/g for decimals
Use two regular expressions, one to match the decimal portion, and a second to do a replace on it.
function format(num) {
return num.toString().replace(/^[+-]?\d+/, function(int) {
return int.replace(/(\d)(?=(\d{3})+$)/g, '$1,');
});
}
console.log(format(332432432))
console.log(format(332432432.3432432))
console.log(format(-332432432))
console.log(format(1E6))
console.log(format(1E-6))
function numberWithCommas(x) {
return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
}
var num=numberWithCommas(2000000); //any number
console.log(num);
enter code here
Try this
// You might want to take decimals into account
Number.prototype.commas= function(){
var s= '', temp,
num= this.toString().split('.'), n=num[0];
while(n.length> 3){
temp= n.substring(n.length-3);
s= ','+temp+s;
n= n.slice(0, -3);
}
if(n) s= n+s;
if(num[1]) s+='.'+num[1];
return s;
}
var n= 10000000000.34;
n.commas() = returned value: (String) 10,000,000,000.34
underscore.string has a nice implementation.
I've amended it slightly to accept numeric strings.
function numberFormat(number, dec, dsep, tsep) {
if (isNaN(number) || number == null) return '';
number = parseFloat(number).toFixed(~~dec);
tsep = typeof tsep == 'string' ? tsep : ',';
var parts = number.split('.'),
fnums = parts[0],
decimals = parts[1] ? (dsep || '.') + parts[1] : '';
return fnums.replace(/(\d)(?=(?:\d{3})+$)/g, '$1' + tsep) + decimals;
}
console.log(numberFormat(123456789))
console.log(numberFormat(123456789.123456789))
console.log(numberFormat(-123456789))
console.log(numberFormat(1E6))
console.log(numberFormat(1E-6))
console.log('---')
console.log(numberFormat(123456789, 6, ',', '_'))
console.log(numberFormat(123456789.123456789, 6, ',', '_'))
console.log(numberFormat(-123456789, 6, ',', '_'))
console.log(numberFormat(1E6, 6, ',', '_'))
console.log(numberFormat(1E-6, 6, ',', '_'))
One RegExp for integers and decimals:
// Formats number 1234.5678 into string "1 234.5678".
function formatNumber(number: number): string {
return number.toString().replace(/(?<!(\.\d*|^.{0}))(?=(\d{3})+(?!\d))/g, ' ');
}
console.log(formatNumber(1234.5678)); // "1 234.5678"
console.log(formatNumber(123)); // "123"
console.log(formatNumber(123.45678)); // "123.45678"
console.log(formatNumber(123456789.11111111)); // "123 456 789.1111111"
Try something like this:
function add_commas(numStr)
{
numStr += '';
var x = numStr.split('.');
var x1 = x[0];
var x2 = x.length > 1 ? '.' + x[1] : '';
var rgx = /(\d+)(\d{3})/;
while (rgx.test(x1)) {
x1 = x1.replace(rgx, '$1' + ',' + '$2');
}
return x1 + x2;
}
If you really want a regex, you can use two in a while loop:
while(num.match(/\d{4}/)) {
num = num.replace(/(\d{3})(,\d|$)/, ',$1$2');
}
And if you want to be fancy, you can format numbers with decimal points too:
while(num.match(/\d{4}(\,|\.)/)) {
num = num.replace(/(\d{3})(,\d|$|\.)/, ',$1$2');
}
Edit:
You can also do this with 2 regular expressions and no loop, splits, joins, etc:
num = num.replace(/(\d{1,2}?)((\d{3})+)$/, "$1,$2");
num = num.replace(/(\d{3})(?=\d)/g, "$1,");
The first regex puts a comma after the first 1 or 2 digits if the remaining number of digits is divisible by three. The second regex places a comma after every remaining group of 3 digits.
These won't work with decimals, but they work great for positive and negative integers.
Test output:
45
3,856
398,868,483,992
635
12,358,717,859,918,856
-1,388,488,184
Someone mentioned that lookbehind isn't possible in Javascript RegExp. Here is a great page that explains how to use lookaround (lookahead and lookbehind).
http://www.regular-expressions.info/lookaround.html
I think you would necessarily have to do multiple passes to achieve this with regular expressions. Try the following:
Run a regex for one digit followed by 3 digits.
If that regex matches, replace it with the first digit, then a comma, then the next 3 digits.
Repeat until (1) finds no matches.
Iteration isn't necessary
function formatNumber(n, separator) {
separator = separator || ",";
n = n.toString()
.split("").reverse().join("")
.replace(/(\d{3})/g, "$1" + separator)
.split("").reverse().join("");
// Strings that have a length that is a multiple of 3 will have a leading separator
return n[0] == separator ? n.substr(1) : n;
}
var testCases = [1, 45, 2856, 398868483992];
for ( var i in testCases ) {
if ( !ns.hasOwnProperty(i) ) { continue; }
console.info(testCases[i]);
console.log(formatNumber(testCases[i]));
}
Results
1
1
45
45
2856
2,856
398868483992
398,868,483,992
First reverse a character array, then add commas after every third number unless it's just before the end of the string or before a - sign. Then reverse the character array again and make it a string again.
function add_commas(numStr){
return numStr.split('').reverse().join('').replace(/(\d{3})(?=[^$|^-])/g, "$1,").split('').reverse().join('');
}
Brandon,
I didn't see too many answers working the regex from the decimal point back, so I thought I might chime in.
I wondered if there is any elegant benefit to re-writing the regexp to scan from the back forward...
function addCommas(inputText) {
// pattern works from right to left
var commaPattern = /(\d+)(\d{3})(\.\d*)*$/;
var callback = function (match, p1, p2, p3) {
return p1.replace(commaPattern, callback) + ',' + p2 + (p3 || '');
};
return inputText.replace(commaPattern, callback);
}
>> Fiddle Demo <<
This accounts for any decimal place.
After so much searching, I generate a regex which accepts all formats
(\d+[-, ,(]{0,3}\d+[-, ,(,)]{0,3}\d+[-, ,(,)]{0,3}\d+[)]{0,2})
Related
I have a string, 12345.00, and I would like it to return 12345.0.
I have looked at trim, but it looks like it is only trimming whitespace and slice which I don't see how this would work. Any suggestions?
You can use the substring function:
let str = "12345.00";
str = str.substring(0, str.length - 1);
console.log(str);
This is the accepted answer, but as per the conversations below, the slice syntax is much clearer:
let str = "12345.00";
str = str.slice(0, -1);
console.log(str);
You can use slice! You just have to make sure you know how to use it. Positive #s are relative to the beginning, negative numbers are relative to the end.
js>"12345.00".slice(0,-1)
12345.0
You can use the substring method of JavaScript string objects:
s = s.substring(0, s.length - 4)
It unconditionally removes the last four characters from string s.
However, if you want to conditionally remove the last four characters, only if they are exactly _bar:
var re = /_bar$/;
s.replace(re, "");
The easiest method is to use the slice method of the string, which allows negative positions (corresponding to offsets from the end of the string):
const s = "your string";
const withoutLastFourChars = s.slice(0, -4);
If you needed something more general to remove everything after (and including) the last underscore, you could do the following (so long as s is guaranteed to contain at least one underscore):
const s = "your_string";
const withoutLastChunk = s.slice(0, s.lastIndexOf("_"));
console.log(withoutLastChunk);
For a number like your example, I would recommend doing this over substring:
console.log(parseFloat('12345.00').toFixed(1));
Do note that this will actually round the number, though, which I would imagine is desired but maybe not:
console.log(parseFloat('12345.46').toFixed(1));
Be aware that String.prototype.{ split, slice, substr, substring } operate on UTF-16 encoded strings
None of the previous answers are Unicode-aware.
Strings are encoded as UTF-16 in most modern JavaScript engines, but higher Unicode code points require surrogate pairs, so older, pre-existing string methods operate on UTF-16 code units, not Unicode code points.
See: Do NOT use .split('').
const string = "ẞ🦊";
console.log(string.slice(0, -1)); // "ẞ\ud83e"
console.log(string.substr(0, string.length - 1)); // "ẞ\ud83e"
console.log(string.substring(0, string.length - 1)); // "ẞ\ud83e"
console.log(string.replace(/.$/, "")); // "ẞ\ud83e"
console.log(string.match(/(.*).$/)[1]); // "ẞ\ud83e"
const utf16Chars = string.split("");
utf16Chars.pop();
console.log(utf16Chars.join("")); // "ẞ\ud83e"
In addition, RegExp methods, as suggested in older answers, don’t match line breaks at the end:
const string = "Hello, world!\n";
console.log(string.replace(/.$/, "").endsWith("\n")); // true
console.log(string.match(/(.*).$/) === null); // true
Use the string iterator to iterate characters
Unicode-aware code utilizes the string’s iterator; see Array.from and ... spread.
string[Symbol.iterator] can be used (e.g. instead of string) as well.
Also see How to split Unicode string to characters in JavaScript.
Examples:
const string = "ẞ🦊";
console.log(Array.from(string).slice(0, -1).join("")); // "ẞ"
console.log([
...string
].slice(0, -1).join("")); // "ẞ"
Use the s and u flags on a RegExp
The dotAll or s flag makes . match line break characters, the unicode or u flag enables certain Unicode-related features.
Note that, when using the u flag, you eliminate unnecessary identity escapes, as these are invalid in a u regex, e.g. \[ is fine, as it would start a character class without the backslash, but \: isn’t, as it’s a : with or without the backslash, so you need to remove the backslash.
Examples:
const unicodeString = "ẞ🦊",
lineBreakString = "Hello, world!\n";
console.log(lineBreakString.replace(/.$/s, "").endsWith("\n")); // false
console.log(lineBreakString.match(/(.*).$/s) === null); // false
console.log(unicodeString.replace(/.$/su, "")); // ẞ
console.log(unicodeString.match(/(.*).$/su)[1]); // ẞ
// Now `split` can be made Unicode-aware:
const unicodeCharacterArray = unicodeString.split(/(?:)/su),
lineBreakCharacterArray = lineBreakString.split(/(?:)/su);
unicodeCharacterArray.pop();
lineBreakCharacterArray.pop();
console.log(unicodeCharacterArray.join("")); // "ẞ"
console.log(lineBreakCharacterArray.join("").endsWith("\n")); // false
Note that some graphemes consist of more than one code point, e.g. 🏳️🌈 which consists of the sequence 🏳 (U+1F3F3), VS16 (U+FE0F), ZWJ (U+200D), 🌈 (U+1F308).
Here, even Array.from will split this into four “characters”.
Matching those is made easier with the RegExp set notation and properties of strings proposal.
Using JavaScript's slice function:
let string = 'foo_bar';
string = string.slice(0, -4); // Slice off last four characters here
console.log(string);
This could be used to remove '_bar' at end of a string, of any length.
A regular expression is what you are looking for:
let str = "foo_bar";
console.log(str.replace(/_bar$/, ""));
Try this:
const myString = "Hello World!";
console.log(myString.slice(0, -1));
Performance
Today 2020.05.13 I perform tests of chosen solutions on Chrome v81.0, Safari v13.1 and Firefox v76.0 on MacOs High Sierra v10.13.6.
Conclusions
the slice(0,-1)(D) is fast or fastest solution for short and long strings and it is recommended as fast cross-browser solution
solutions based on substring (C) and substr(E) are fast
solutions based on regular expressions (A,B) are slow/medium fast
solutions B, F and G are slow for long strings
solution F is slowest for short strings, G is slowest for long strings
Details
I perform two tests for solutions A, B, C, D, E(ext), F, G(my)
for 8-char short string (from OP question) - you can run it HERE
for 1M long string - you can run it HERE
Solutions are presented in below snippet
function A(str) {
return str.replace(/.$/, '');
}
function B(str) {
return str.match(/(.*).$/)[1];
}
function C(str) {
return str.substring(0, str.length - 1);
}
function D(str) {
return str.slice(0, -1);
}
function E(str) {
return str.substr(0, str.length - 1);
}
function F(str) {
let s= str.split("");
s.pop();
return s.join("");
}
function G(str) {
let s='';
for(let i=0; i<str.length-1; i++) s+=str[i];
return s;
}
// ---------
// TEST
// ---------
let log = (f)=>console.log(`${f.name}: ${f("12345.00")}`);
[A,B,C,D,E,F,G].map(f=>log(f));
This snippet only presents soutions
Here are example results for Chrome for short string
Use regex:
let aStr = "12345.00";
aStr = aStr.replace(/.$/, '');
console.log(aStr);
How about:
let myString = "12345.00";
console.log(myString.substring(0, myString.length - 1));
1. (.*), captures any character multiple times:
console.log("a string".match(/(.*).$/)[1]);
2. ., matches last character, in this case:
console.log("a string".match(/(.*).$/));
3. $, matches the end of the string:
console.log("a string".match(/(.*).{2}$/)[1]);
https://stackoverflow.com/questions/34817546/javascript-how-to-delete-last-two-characters-in-a-string
Just use trim if you don't want spaces
"11.01 °C".slice(0,-2).trim()
Here is an alternative that i don't think i've seen in the other answers, just for fun.
var strArr = "hello i'm a string".split("");
strArr.pop();
document.write(strArr.join(""));
Not as legible or simple as slice or substring but does allow you to play with the string using some nice array methods, so worth knowing.
debris = string.split("_") //explode string into array of strings indexed by "_"
debris.pop(); //pop last element off the array (which you didn't want)
result = debris.join("_"); //fuse the remainng items together like the sun
If you want to do generic rounding of floats, instead of just trimming the last character:
var float1 = 12345.00,
float2 = 12345.4567,
float3 = 12345.982;
var MoreMath = {
/**
* Rounds a value to the specified number of decimals
* #param float value The value to be rounded
* #param int nrDecimals The number of decimals to round value to
* #return float value rounded to nrDecimals decimals
*/
round: function (value, nrDecimals) {
var x = nrDecimals > 0 ? 10 * parseInt(nrDecimals, 10) : 1;
return Math.round(value * x) / x;
}
}
MoreMath.round(float1, 1) => 12345.0
MoreMath.round(float2, 1) => 12345.5
MoreMath.round(float3, 1) => 12346.0
EDIT: Seems like there exists a built in function for this, as Paolo points out. That solution is obviously much cleaner than mine. Use parseFloat followed by toFixed
if(str.substring(str.length - 4) == "_bar")
{
str = str.substring(0, str.length - 4);
}
Via slice(indexStart, indexEnd) method - note, this does NOT CHANGE the existing string, it creates a copy and changes the copy.
console.clear();
let str = "12345.00";
let a = str.slice(0, str.length -1)
console.log(a, "<= a");
console.log(str, "<= str is NOT changed");
Via Regular Expression method - note, this does NOT CHANGE the existing string, it creates a copy and changes the copy.
console.clear();
let regExp = /.$/g
let b = str.replace(regExp,"")
console.log(b, "<= b");
console.log(str, "<= str is NOT changed");
Via array.splice() method -> this only works on arrays, and it CHANGES, the existing array (so careful with this one), you'll need to convert a string to an array first, then back.
console.clear();
let str = "12345.00";
let strToArray = str.split("")
console.log(strToArray, "<= strToArray");
let spliceMethod = strToArray.splice(str.length-1, 1)
str = strToArray.join("")
console.log(str, "<= str is changed now");
In cases where you want to remove something that is close to the end of a string (in case of variable sized strings) you can combine slice() and substr().
I had a string with markup, dynamically built, with a list of anchor tags separated by comma. The string was something like:
var str = "<a>text 1,</a><a>text 2,</a><a>text 2.3,</a><a>text abc,</a>";
To remove the last comma I did the following:
str = str.slice(0, -5) + str.substr(-4);
You can, in fact, remove the last arr.length - 2 items of an array using arr.length = 2, which if the array length was 5, would remove the last 3 items.
Sadly, this does not work for strings, but we can use split() to split the string, and then join() to join the string after we've made any modifications.
var str = 'string'
String.prototype.removeLast = function(n) {
var string = this.split('')
string.length = string.length - n
return string.join('')
}
console.log(str.removeLast(3))
Try to use toFixed
const str = "12345.00";
return (+str).toFixed(1);
Try this:
<script>
var x="foo_foo_foo_bar";
for (var i=0; i<=x.length; i++) {
if (x[i]=="_" && x[i+1]=="b") {
break;
}
else {
document.write(x[i]);
}
}
</script>
You can also try the live working example on http://jsfiddle.net/informativejavascript/F7WTn/87/.
#Jason S:
You can use slice! You just have to
make sure you know how to use it.
Positive #s are relative to the
beginning, negative numbers are
relative to the end.
js>"12345.00".slice(0,-1)
12345.0
Sorry for my graphomany but post was tagged 'jquery' earlier. So, you can't use slice() inside jQuery because slice() is jQuery method for operations with DOM elements, not substrings ...
In other words answer #Jon Erickson suggest really perfect solution.
However, your method will works out of jQuery function, inside simple Javascript.
Need to say due to last discussion in comments, that jQuery is very much more often renewable extension of JS than his own parent most known ECMAScript.
Here also exist two methods:
as our:
string.substring(from,to) as plus if 'to' index nulled returns the rest of string. so:
string.substring(from) positive or negative ...
and some other - substr() - which provide range of substring and 'length' can be positive only:
string.substr(start,length)
Also some maintainers suggest that last method string.substr(start,length) do not works or work with error for MSIE.
Use substring to get everything to the left of _bar. But first you have to get the instr of _bar in the string:
str.substring(3, 7);
3 is that start and 7 is the length.
I use the following function to format numbers:
function formatNumber(value, precision) {
if (Number.isFinite(value)) {
// Source: kalisjoshua's comment to VisioN's answer in the following stackoverflow question:
// http://stackoverflow.com/questions/149055/how-can-i-format-numbers-as-money-in-javascript
return value.toFixed(precision || 0).replace(/(\d)(?=(\d{3})+(?:\.\d+)?$)/g, "$1,")
} else {
return ""
}
}
The above works except one case:
1130.000200 becomes 1,130.000,200
but I need
1130.000200 become 1,130.000200
It seems I need negative lookbehind ?<!, i.e. match a digit not preceded by dot, but how?
EDIT: As answered in this question, Number.prototype.toLocaleString() is a good solution for newer browsers. I need to support IE10, so leave this question as it is here.
You can use this simple function to format your decimal numbers:
function fmt(num) {
// split into two; integer and fraction part
var arr = num.match(/^(\d+)((?:\.\d+)?)$/);
// format integer part and append fraction part
return arr[1].replace(/(\d)(?=(?:\d{3})+$)/g, '$1,') + arr[2];
}
var s1 = fmt('1130.000200')
//=> "1,130.000200"
var s2 = fmt('1130000200')
//=> "1,130,000,200"
Simply remove ? in after the .Match. updated pattern is /(\d)(?=(\d{3})+(?:\.\d+)$)/g,
? Quantifier — Matches between zero and one times, as many times as
possible, giving back as needed
Demo regex and explanation
console.log('1130.000200'.replace(/(\d)(?=(\d{3})+(?:\.\d+)$)/g, "$1,"))
Made it work with code below.
The key is to match decimal point which is variable d. If not matches, don't replace.
function formatNumber(value, precision) {
var regex = /(\d)(?=(\d{3})+(?:(\.)\d+)?$)/g;
return (+value).toFixed(precision || 0).replace(regex, function(a, b, c, d) {
return d ? b+',' : b;
});
}
console.log(formatNumber(1130.000200, 6));
console.log(formatNumber(1130, 6));
Example from regex101, you'll see decimal point matches into Group 3. https://regex101.com/r/qxriNx/1
I have a string, 12345.00, and I would like it to return 12345.0.
I have looked at trim, but it looks like it is only trimming whitespace and slice which I don't see how this would work. Any suggestions?
You can use the substring function:
let str = "12345.00";
str = str.substring(0, str.length - 1);
console.log(str);
This is the accepted answer, but as per the conversations below, the slice syntax is much clearer:
let str = "12345.00";
str = str.slice(0, -1);
console.log(str);
You can use slice! You just have to make sure you know how to use it. Positive #s are relative to the beginning, negative numbers are relative to the end.
js>"12345.00".slice(0,-1)
12345.0
You can use the substring method of JavaScript string objects:
s = s.substring(0, s.length - 4)
It unconditionally removes the last four characters from string s.
However, if you want to conditionally remove the last four characters, only if they are exactly _bar:
var re = /_bar$/;
s.replace(re, "");
The easiest method is to use the slice method of the string, which allows negative positions (corresponding to offsets from the end of the string):
const s = "your string";
const withoutLastFourChars = s.slice(0, -4);
If you needed something more general to remove everything after (and including) the last underscore, you could do the following (so long as s is guaranteed to contain at least one underscore):
const s = "your_string";
const withoutLastChunk = s.slice(0, s.lastIndexOf("_"));
console.log(withoutLastChunk);
For a number like your example, I would recommend doing this over substring:
console.log(parseFloat('12345.00').toFixed(1));
Do note that this will actually round the number, though, which I would imagine is desired but maybe not:
console.log(parseFloat('12345.46').toFixed(1));
Be aware that String.prototype.{ split, slice, substr, substring } operate on UTF-16 encoded strings
None of the previous answers are Unicode-aware.
Strings are encoded as UTF-16 in most modern JavaScript engines, but higher Unicode code points require surrogate pairs, so older, pre-existing string methods operate on UTF-16 code units, not Unicode code points.
See: Do NOT use .split('').
const string = "ẞ🦊";
console.log(string.slice(0, -1)); // "ẞ\ud83e"
console.log(string.substr(0, string.length - 1)); // "ẞ\ud83e"
console.log(string.substring(0, string.length - 1)); // "ẞ\ud83e"
console.log(string.replace(/.$/, "")); // "ẞ\ud83e"
console.log(string.match(/(.*).$/)[1]); // "ẞ\ud83e"
const utf16Chars = string.split("");
utf16Chars.pop();
console.log(utf16Chars.join("")); // "ẞ\ud83e"
In addition, RegExp methods, as suggested in older answers, don’t match line breaks at the end:
const string = "Hello, world!\n";
console.log(string.replace(/.$/, "").endsWith("\n")); // true
console.log(string.match(/(.*).$/) === null); // true
Use the string iterator to iterate characters
Unicode-aware code utilizes the string’s iterator; see Array.from and ... spread.
string[Symbol.iterator] can be used (e.g. instead of string) as well.
Also see How to split Unicode string to characters in JavaScript.
Examples:
const string = "ẞ🦊";
console.log(Array.from(string).slice(0, -1).join("")); // "ẞ"
console.log([
...string
].slice(0, -1).join("")); // "ẞ"
Use the s and u flags on a RegExp
The dotAll or s flag makes . match line break characters, the unicode or u flag enables certain Unicode-related features.
Note that, when using the u flag, you eliminate unnecessary identity escapes, as these are invalid in a u regex, e.g. \[ is fine, as it would start a character class without the backslash, but \: isn’t, as it’s a : with or without the backslash, so you need to remove the backslash.
Examples:
const unicodeString = "ẞ🦊",
lineBreakString = "Hello, world!\n";
console.log(lineBreakString.replace(/.$/s, "").endsWith("\n")); // false
console.log(lineBreakString.match(/(.*).$/s) === null); // false
console.log(unicodeString.replace(/.$/su, "")); // ẞ
console.log(unicodeString.match(/(.*).$/su)[1]); // ẞ
// Now `split` can be made Unicode-aware:
const unicodeCharacterArray = unicodeString.split(/(?:)/su),
lineBreakCharacterArray = lineBreakString.split(/(?:)/su);
unicodeCharacterArray.pop();
lineBreakCharacterArray.pop();
console.log(unicodeCharacterArray.join("")); // "ẞ"
console.log(lineBreakCharacterArray.join("").endsWith("\n")); // false
Note that some graphemes consist of more than one code point, e.g. 🏳️🌈 which consists of the sequence 🏳 (U+1F3F3), VS16 (U+FE0F), ZWJ (U+200D), 🌈 (U+1F308).
Here, even Array.from will split this into four “characters”.
Matching those is made easier with the RegExp set notation and properties of strings proposal.
Using JavaScript's slice function:
let string = 'foo_bar';
string = string.slice(0, -4); // Slice off last four characters here
console.log(string);
This could be used to remove '_bar' at end of a string, of any length.
A regular expression is what you are looking for:
let str = "foo_bar";
console.log(str.replace(/_bar$/, ""));
Try this:
const myString = "Hello World!";
console.log(myString.slice(0, -1));
Performance
Today 2020.05.13 I perform tests of chosen solutions on Chrome v81.0, Safari v13.1 and Firefox v76.0 on MacOs High Sierra v10.13.6.
Conclusions
the slice(0,-1)(D) is fast or fastest solution for short and long strings and it is recommended as fast cross-browser solution
solutions based on substring (C) and substr(E) are fast
solutions based on regular expressions (A,B) are slow/medium fast
solutions B, F and G are slow for long strings
solution F is slowest for short strings, G is slowest for long strings
Details
I perform two tests for solutions A, B, C, D, E(ext), F, G(my)
for 8-char short string (from OP question) - you can run it HERE
for 1M long string - you can run it HERE
Solutions are presented in below snippet
function A(str) {
return str.replace(/.$/, '');
}
function B(str) {
return str.match(/(.*).$/)[1];
}
function C(str) {
return str.substring(0, str.length - 1);
}
function D(str) {
return str.slice(0, -1);
}
function E(str) {
return str.substr(0, str.length - 1);
}
function F(str) {
let s= str.split("");
s.pop();
return s.join("");
}
function G(str) {
let s='';
for(let i=0; i<str.length-1; i++) s+=str[i];
return s;
}
// ---------
// TEST
// ---------
let log = (f)=>console.log(`${f.name}: ${f("12345.00")}`);
[A,B,C,D,E,F,G].map(f=>log(f));
This snippet only presents soutions
Here are example results for Chrome for short string
Use regex:
let aStr = "12345.00";
aStr = aStr.replace(/.$/, '');
console.log(aStr);
How about:
let myString = "12345.00";
console.log(myString.substring(0, myString.length - 1));
1. (.*), captures any character multiple times:
console.log("a string".match(/(.*).$/)[1]);
2. ., matches last character, in this case:
console.log("a string".match(/(.*).$/));
3. $, matches the end of the string:
console.log("a string".match(/(.*).{2}$/)[1]);
https://stackoverflow.com/questions/34817546/javascript-how-to-delete-last-two-characters-in-a-string
Just use trim if you don't want spaces
"11.01 °C".slice(0,-2).trim()
Here is an alternative that i don't think i've seen in the other answers, just for fun.
var strArr = "hello i'm a string".split("");
strArr.pop();
document.write(strArr.join(""));
Not as legible or simple as slice or substring but does allow you to play with the string using some nice array methods, so worth knowing.
debris = string.split("_") //explode string into array of strings indexed by "_"
debris.pop(); //pop last element off the array (which you didn't want)
result = debris.join("_"); //fuse the remainng items together like the sun
If you want to do generic rounding of floats, instead of just trimming the last character:
var float1 = 12345.00,
float2 = 12345.4567,
float3 = 12345.982;
var MoreMath = {
/**
* Rounds a value to the specified number of decimals
* #param float value The value to be rounded
* #param int nrDecimals The number of decimals to round value to
* #return float value rounded to nrDecimals decimals
*/
round: function (value, nrDecimals) {
var x = nrDecimals > 0 ? 10 * parseInt(nrDecimals, 10) : 1;
return Math.round(value * x) / x;
}
}
MoreMath.round(float1, 1) => 12345.0
MoreMath.round(float2, 1) => 12345.5
MoreMath.round(float3, 1) => 12346.0
EDIT: Seems like there exists a built in function for this, as Paolo points out. That solution is obviously much cleaner than mine. Use parseFloat followed by toFixed
if(str.substring(str.length - 4) == "_bar")
{
str = str.substring(0, str.length - 4);
}
Via slice(indexStart, indexEnd) method - note, this does NOT CHANGE the existing string, it creates a copy and changes the copy.
console.clear();
let str = "12345.00";
let a = str.slice(0, str.length -1)
console.log(a, "<= a");
console.log(str, "<= str is NOT changed");
Via Regular Expression method - note, this does NOT CHANGE the existing string, it creates a copy and changes the copy.
console.clear();
let regExp = /.$/g
let b = str.replace(regExp,"")
console.log(b, "<= b");
console.log(str, "<= str is NOT changed");
Via array.splice() method -> this only works on arrays, and it CHANGES, the existing array (so careful with this one), you'll need to convert a string to an array first, then back.
console.clear();
let str = "12345.00";
let strToArray = str.split("")
console.log(strToArray, "<= strToArray");
let spliceMethod = strToArray.splice(str.length-1, 1)
str = strToArray.join("")
console.log(str, "<= str is changed now");
In cases where you want to remove something that is close to the end of a string (in case of variable sized strings) you can combine slice() and substr().
I had a string with markup, dynamically built, with a list of anchor tags separated by comma. The string was something like:
var str = "<a>text 1,</a><a>text 2,</a><a>text 2.3,</a><a>text abc,</a>";
To remove the last comma I did the following:
str = str.slice(0, -5) + str.substr(-4);
You can, in fact, remove the last arr.length - 2 items of an array using arr.length = 2, which if the array length was 5, would remove the last 3 items.
Sadly, this does not work for strings, but we can use split() to split the string, and then join() to join the string after we've made any modifications.
var str = 'string'
String.prototype.removeLast = function(n) {
var string = this.split('')
string.length = string.length - n
return string.join('')
}
console.log(str.removeLast(3))
Try to use toFixed
const str = "12345.00";
return (+str).toFixed(1);
Try this:
<script>
var x="foo_foo_foo_bar";
for (var i=0; i<=x.length; i++) {
if (x[i]=="_" && x[i+1]=="b") {
break;
}
else {
document.write(x[i]);
}
}
</script>
You can also try the live working example on http://jsfiddle.net/informativejavascript/F7WTn/87/.
#Jason S:
You can use slice! You just have to
make sure you know how to use it.
Positive #s are relative to the
beginning, negative numbers are
relative to the end.
js>"12345.00".slice(0,-1)
12345.0
Sorry for my graphomany but post was tagged 'jquery' earlier. So, you can't use slice() inside jQuery because slice() is jQuery method for operations with DOM elements, not substrings ...
In other words answer #Jon Erickson suggest really perfect solution.
However, your method will works out of jQuery function, inside simple Javascript.
Need to say due to last discussion in comments, that jQuery is very much more often renewable extension of JS than his own parent most known ECMAScript.
Here also exist two methods:
as our:
string.substring(from,to) as plus if 'to' index nulled returns the rest of string. so:
string.substring(from) positive or negative ...
and some other - substr() - which provide range of substring and 'length' can be positive only:
string.substr(start,length)
Also some maintainers suggest that last method string.substr(start,length) do not works or work with error for MSIE.
Use substring to get everything to the left of _bar. But first you have to get the instr of _bar in the string:
str.substring(3, 7);
3 is that start and 7 is the length.
I've have a input string:
12345,3244,654,ffgv,87676,988ff,87657
I'm having a difficulty to transform all terms in the string that are not five digit numbers to a constant 34567 using regular expressions. So, the output would be like this:
12345,34567,34567,34567,87676,34567,87657
For this, I looked at two options:
negated character class: Not useful because it does not execute directly on this expression ,[^\d{5}],
lookahead and lookbehind: Issue here is that it doesn't include non-matched part in the result of this expression ,(?!\d{5}) or (?<!\d{5}), for the purpose of substitution/replace.
Once the desired expression is found, it would give a result so that one can replace non-matched part using tagged regions like \1, \2.
Is there any mechanism in regular expression tools to achieve the output as mentioned in the above example?
Edit: I really appreciate those who have answered non-regex solutions, but I would be more thankful if you provide a regex-based solution.
You don't need regex for this. You can use str.split to split the string at commas first and then for each item check if its length is greater than or equal to 5 and it contains only digits(using str.isdigit). Lastly combine all the items using str.join.
>>> s = '12345,3244,654,ffgv,87676,988ff,87657'
>>> ','.join(x if len(x) >= 5 and x.isdigit() else '34567' for x in s.split(','))
'12345,34567,34567,34567,87676,34567,87657'
Javascript version:
function isdigit(s){
for(var i=0; i <s.length; i++){
if(!(s[i] >= '0' && s[i] <= '9')){
return false;
}
}
return true;
}
arr = "12345,3244,654,ffgv,87676,988ff,87657".split(",");
for(var i=0; i < arr.length; i++){
if(arr[i].length < 5 || ! isdigit(arr[i])) arr[i] = '34567';
}
output = arr.join(",")
Try the following: /\b(?!\d{5})[^,]+\b/g
It constrains the expression between word boundaries (\b),
Followed by a negative look-ahead for non five digit numbers (!\d{5}),
Followed by any characters between ,
const expression = /\b(?!\d{5})[^,]+\b/g;
const input = '12345,3244,654,ffgv,87676,988ff,87657';
const expectedOutput = '12345,34567,34567,34567,87676,34567,87657';
const output = input.replace(expression, '34567');
console.log(output === expectedOutput, expectedOutput, output);
This approach uses /\b(\d{5})|(\w+)\b/g:
we match on boundaries (\b)
our first capture group captures "good strings"
our looser capture group gets the leftovers (bad strings)
our replacer() function knows the difference
const str = '12345,3244,654,ffgv,87676,988ff,87657';
const STAND_IN = '34567';
const massageString = (str) => {
const pattern = /\b(\d{5})|(\w+)\b/g;
const replacer = (match, goodstring, badstring) => {
if (goodstring) {
return goodstring;
} else {
return STAND_IN;
}
}
const r = str.replace(pattern,replacer);
return r;
};
console.log( massageString(str) );
I think the following would work for value no longer than 5 alphanumeric characters:
(,(?!\d{5})\w{1,5})
if longer than 5 alphanumeric characters, then remove 5 in above expression:
(,(?!\d{5})\w{1,})
and you can replace using:
,34567
You can see a demo on regex101. Of course, there might be faster non-regex methods for specific languages as well (python, perl or JS)
I have a string like
:21::22::24::99:
And I want to find say if :22: is in said string. But is there a means of searching a string like above for one like I want to match it to with javascript, and if there is, does it involve regex magic or is there something else? Either way not sure how to do it, more so if regex is involved.
You can build the regular expression you need:
function findNumberInString(num, s) {
var re = new RegExp(':' + num + ':');
return re.test(s);
}
var s = ':21::22::24::99';
var n = '22';
findNumberInString(n, s); // true
or just use match (though test is cleaner to me)
!!s.match(':' + n + ':'); // true
Edit
Both the above use regular expressions, so a decimal ponit (.) will come to represent any character, so "4.1" will match "461" or even "4z1", so better to use a method based on String.prototype.indexOf just in case (unless you want "." to represent any character), so per Blender's comment:
function findNumberInString(num, s) {
return s.indexOf(':' + num + ':') != -1;
}
like this:
aStr = ':21::22::24::99:';
if(aStr.indexOf(':22:') != -1){
//':22:' exists in aStr
}
else{
//it doesn't
}