Search code examples
javascriptregextrim

Left Trim in Javascript

There are a lot of scripts out there to trim a string in JavaScript, but none that allow you to just left trim a string.

This is what I use to trim:

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

I would like to change this a little and create a new function called leftTrim that only removes the leading space.

Solution

  • Use:

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

    In the regex the:

    • ^ means "from the beginning of the string"
    • \s means whitespace character class
    • + means one-or more (greedy)

    so....

    • ^\s+ means "one or more consecutive whitespace characters from the beginning of the class"

    Note: The g flag at the end of your regex is unnecessary as the anchors (^ and $) explicitly define what will match. There cannot be multiple matches.

    See https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/RegExp for details on regex syntax in javascript