Thursday, May 31, 2012

Convert JavaScript String to be all lower case?

How can I convert a JavaScript string value to be in all lower case letters?

Example: "Your Name" to "your name".

Source: Tips4all


  1. "Your Name".toLowerCase();

  2. Use either toLowerCase or toLocaleLowerCase methods of the String object. The difference is that toLocaleLowerCase will take current locale of the user/host into account. As per § of the ECMAScript Language Specification (ECMA-262), toLocaleLowerCase…

    …works exactly the same as toLowerCase
    except that its result is intended to
    yield the correct result for the host
    environment’s current locale, rather
    than a locale-independent result.
    There will only be a difference in the
    few cases (such as Turkish) where the
    rules for that language conflict with
    the regular Unicode case mappings.


    var lower = 'Your Name'.toLowerCase();

    Also note that the toLowerCase and toLocaleLowerCase functions are implemented to work generically on any value type. Therefore you can invoke these functions even on non-String objects. Doing so will imply automatic conversion to a string value prior to changing the case of each character in the resulting string value. For example, you can apply toLowerCase directly on a date like this:

    var lower = String.prototype.toLowerCase.apply(new Date());

    and which is effectively equivalent to:

    var lower = new Date().toString().toLowerCase();

    The second form is generally preferred for its simplicity and readability, but the first has the benefit that it can work with a null value as well while the second requires a string. The result of applying toLowerCase or toLocaleLowerCase on null is null (and not an error condition). The first form may therefore come handy in some generic-handling code.

  3. Yes, any string in JavaScript has a toLowerCase() method that will return a new string that is the old string in all lower case. The old string will remain unchanged.

    So, you can do something like:


  4. toLocaleUpperCase() or lower case functions don't behave like they should do. For example in my system, Safari 4, Chrome 4 Beta, Firefox 3.5.x it converts strings with Turkish characters incorrectly. The browsers respond to navigator.language as "en-US", "tr", "en-US" respectively. But there is no way to get user's Accept-Lang setting in the browser as far as I could find. Only Chrome gives me tr although I have configured every browser as tr-TR locale preferred. I think these settings only affect HTTP header, but we can't access to these settings via JS.
    In the Mozilla documentation it says "The characters within a string are converted to ... while respecting the current locale. For most languages, this will return the same as ...". I think it's valid for Turkish, it doesn't differ it's configured as en or tr. In Turkish it should convert "DİNÇ" to "dinç" and "DINÇ" to "dınç" or vice-versa.

  5. example

    <script type="text/javascript">
    var yourstring = 'Your Name'
    var lowercase = yourstring.toLowerCase();
    document.write('original string:<b> ' + yourstring + '</b><br>');
    document.write('converted sting <b>' + lowercase + '</b>');

    try it on

  6. I payed attention that lot's are looking for strtolower() function in JavaScript. They are expecting the same function name as in other languages, that's why this post is here.

    I would recommend using native Javascript function

    "SomE StriNg".toLowerCase() method is simplier and faster

    Here's the function that behaves exactly the same as PHP one (for those who are porting PHP code into js)

    function strtolower (str) {
    return (str + '').toLowerCase();

  7. Note that the function will ONLY work on STRING objects.

    For instance, I was consuming a plugin, and was confused why I was getting a
    "extension.tolowercase is not a function" JS error.

    onChange: function(file, extension)
    alert("extension.toLowerCase()=>" + extension.toLowerCase() + "<=");

    Which produced the error "extension.toLowerCase is not a function"
    So I tried this piece of code, which revealed the problem!

    alert("(typeof extension)=>" + (typeof extension) + "<=");;

    The output was"(typeof extension)=>object<=" - so AhHa, I was NOT getting a string var for my input. The fix is straight forward though - just force the darn thing into a String!:

    var extension = String(extension);

    After the cast, the extension.toLowerCase() function worked fine.