Trim string in JavaScript?

Question

How do I trim a string in JavaScript? That is, how do I remove all whitespace from the beginning and the end of the string in JavaScript?

Answer 1

mine uses a single regex to look for cases where trimming is necessary, and uses that regex's results to determine desired substring bounds:

var illmatch= /^(\s*)(?:.*?)(\s*)$/
function strip(me){
    var match= illmatch.exec(me)
    if(match && (match[1].length || match[2].length)){
        me= me.substring(match[1].length, p.length-match[2].length)
    }
    return me
}

the one design decision that went into this was using a substring to perform the final capture. s/\?:// (make the middle term capturing) and and the replacement fragment becomes:

    if(match && (match[1].length || match[3].length)){
        me= match[2]
    }

there's two performance bets I made in these impls:

1. does the substring implementation copy the original string's data? if so, in the first, when a string needs to be trimmed there is a double traversal, first in the regex (which may, hopefully be partial), and second in the substring extraction. hopefully a substring implementation only references the original string, so operations like substring can be nearly free. cross fingers

2. how good is the capture in the regex impl? the middle term, the output value, could potentially be very long. i wasn't ready to bank that all regex impls' capturing wouldn't balk at a couple hundred KB input capture, but i also did not test (too many runtimes, sorry!). the second ALWAYS runs a capture; if your engine can do this without taking a hit, perhaps using some of the above string-roping-techniques, for sure USE IT!

Answer 2

use simply code

var str = "       Hello World!        ";
alert(str.trim());

Browser support

Feature         Chrome  Firefox Internet Explorer   Opera   Safari  Edge
Basic support   (Yes)   3.5     9                   10.5    5       ?

For old browser add prototype

if (!String.prototype.trim) {
  String.prototype.trim = function () {
    return this.replace(/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g, '');
  };
}

Answer 3

There are a lot of implementations that can be used. The most obvious seems to be something like this:

String.prototype.trim = function() {
    return this.replace(/^\s+|\s+$/g, "");
};

" foo bar ".trim();  // "foo bar"

Answer 4

Flagrant Badassery has 11 different trims with benchmark information:

http://blog.stevenlevithan.com/archives/faster-trim-javascript

Non-surprisingly regexp-based are slower than traditional loop.

---

Here is my personal one. This code is old! I wrote it for JavaScript1.1 and Netscape 3 and it has been only slightly updated since. (Original used String.charAt)

/**
 *  Trim string. Actually trims all control characters.
 *  Ignores fancy Unicode spaces. Forces to string.
 */
function trim(str) {
    str = str.toString();
    var begin = 0;
    var end = str.length - 1;
    while (begin <= end && str.charCodeAt(begin) < 33) { ++begin; }
    while (end > begin && str.charCodeAt(end) < 33) { --end; }
    return str.substr(begin, end - begin + 1);
}

Answer 5

Although there are a bunch of correct answers above, it should be noted that the String object in JavaScript has a native .trim() method as of ECMAScript 5. Thus ideally any attempt to prototype the trim method should really check to see if it already exists first.

if(!String.prototype.trim){  
  String.prototype.trim = function(){  
    return this.replace(/^\s+|\s+$/g,'');  
  };  
}

Added natively in: JavaScript 1.8.1 / ECMAScript 5

Thus supported in:

Firefox: 3.5+

Safari: 5+

Internet Explorer: IE9+ (in Standards mode only!) http://blogs.msdn.com/b/ie/archive/2010/06/25/enhanced-scripting-in-ie9-ecmascript-5-support-and-more.aspx

Chrome: 5+

Opera: 10.5+

ECMAScript 5 Support Table: http://kangax.github.com/es5-compat-table/

Answer 6

I had written this function for trim, when the .trim() function was not available in JS way back in 2008. Some of the older browsers still do not support the .trim() function and i hope this function may help somebody.

TRIM FUNCTION

function trim(str)
{
    var startpatt = /^\s/;
    var endpatt = /\s$/;

    while(str.search(startpatt) == 0)
        str = str.substring(1, str.length);

    while(str.search(endpatt) == str.length-1)
        str = str.substring(0, str.length-1);   

    return str;
}

Explanation: The function trim() accept a string object and remove any starting and trailing whitespaces (spaces,tabs and newlines) and return the trimmed string. You can use this function to trim form inputs to ensure valid data to be sent.

The function can be called in the following manner as an example.

form.elements[i].value = trim(form.elements[i].value);