Useful trim prototype (function) in core javascript

Published on Mar 4, 2011 Arvind KumarJavascript2 Comments on Useful trim prototype (function) in core javascript

Below is the most commonly used trim prototype/function in javascript. Posting for reference.

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

You can place the above code (wrapped in <script></script>) inside <header> section of your web page or you can place it in an external javascript file which you include in the header section.

//how to use it example
var my_string = "  Hello trim me           ";
var my_string_trimmed = my_string.trim();
//my_string_trimmed now has "Hello trim me"

Very useful tool.

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2 thoughts on “Useful trim prototype (function) in core javascript”

  1. very bad idea. Modern browsers (ie9, ff, opera, chrome, safari) implement native trim functions.
    test for this prior replacing it:
    if (!String.prototype.trim) {

    Reply

    1. @Holger – I never faced any issue while using this function. Considering the check kind of thing one could modify it to look like:

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

      Also, considering the global pattern delimiter (g) it may be slow sometimes but i don’t see any other ‘bad’ in this implementation. For a faster alternative one may consider using Douglas Crockford’s implementation(regex) which is as following:

      String.prototype.trim = function () {
      return this.replace(/^\s*(\S*(\s+\S+)*)\s*$/, "$1");
      };

      I am not sure what do you mean by “native” trim function in browsers. I could not find such function at least in firefox (which i use most). Can you guide me to find one?

      Reply

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