[javascript] 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"

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 § 15.5.4.17 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.

Example:

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. On earlier versions of IE, the first had the benefit that it could work with a null value. The result of applying toLowerCase or toLocaleLowerCase on null would yield null (and not an error condition).

In case you want to build it yourself:

function toLowerCase(string) {

let lowerCaseString = "";

for (let i = 0; i < string.length; i++) {
    //find ASCII charcode
    let charcode = string.charCodeAt(i);

    //if uppercase
    if (charcode > 64 && charcode < 97){
        //convert to lowercase
        charcode = charcode + 32
    }

    //back to char
    let lowercase = String.fromCharCode(charcode);

    //append
    lowerCaseString = lowerCaseString.concat(lowercase);
}

return lowerCaseString

}

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 trouble 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 "DINÇ" to "dinç" and "DINÇ" to "dinç" or vice-versa.

Method or Function: toLowerCase(), toUpperCase()

Description: These methods are used to cover a string or alphabet from lower case to upper case or vice versa. e.g: "and" to "AND".

Converting to Upper Case:- Example Code:-

<script language=javascript>
var ss = " testing case conversion method ";
var result = ss.toUpperCase();
document.write(result);
</script>

Result: TESTING CASE CONVERSION METHOD

Converting to Lower Case:- Example Code:

<script language=javascript>
var ss = " TESTING LOWERCASE CONVERT FUNCTION ";
var result = ss.toLowerCase();
document.write(result);
</script>

Result: testing lowercase convert function

Explanation: In the above examples,

toUpperCase() method converts any string to "UPPER" case letters.
toLowerCase() method converts any string to "lower" case letters.

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:

"Foo".toLowerCase();
document.getElementById('myField').value.toLowerCase();

Tray this short way

  var lower = (str+"").toLowerCase();

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.

Opt 1: using toLowerCase()

var x = 'ABC';
x = x.toLowerCase();

Opt 2: Using your own function

function convertToLowerCase(str) {
  var result = '';

  for (var i = 0; i < str.length; i++) {
    var code = str.charCodeAt(i);
    if (code > 64 && code < 91) {
      result += String.fromCharCode(code + 32);
    } else {
      result += str.charAt(i);
    }
  }
  return result;
}

Call it as:

x = convertToLowerCase(x);

Just an examples for toLowerCase(), toUpperCase() and prototype for not yet available toTitleCase() or toPropperCase()

String.prototype.toTitleCase = function() {_x000D_
  return this.split(' ').map(i => i[0].toUpperCase() + i.substring(1).toLowerCase()).join(' ');_x000D_
}_x000D_
_x000D_
String.prototype.toPropperCase = function() {_x000D_
  return this.toTitleCase();_x000D_
}_x000D_
_x000D_
var OriginalCase = 'Your Name';_x000D_
var lowercase = OriginalCase.toLowerCase();_x000D_
var upperCase = lowercase.toUpperCase();_x000D_
var titleCase = upperCase.toTitleCase();_x000D_
_x000D_
console.log('Original: ' + OriginalCase);_x000D_
console.log('toLowerCase(): ' + lowercase);_x000D_
console.log('toUpperCase(): ' + upperCase);_x000D_
console.log('toTitleCase(): ' + titleCase);

edited 2018

I payed attention that lots of people are looking for strtolower() 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()

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

function strToLower (str) {
    return String(str).toLowerCase();
}

Simply use JS toLowerCase()
let v = "Your Name" let u = v.toLowerCase(); or
let u = "Your Name".toLowerCase();

Try

<input type="text" style="text-transform: uppercase">  //uppercase
<input type="text" style="text-transform: lowercase">  //lowercase

Demo - JSFiddle

you can use the in built .toLowerCase() method on javascript strings. ex: var x = "Hello"; x.toLowerCase();