JavaScript substring(), substr(), trim(), startsWith() and endsWith()

I've gotten a lot into JavaScript and jQuery development lately.

I love jQuery. So simple and powerful. I used to use Prototype, but the ease of development and jQuery documentation makes it the language of choice for me.

Well, in JS, there's always a need for string manipulation. Coming from a managed code world, I expect certain built-in functions. Here is some examples for functions that you wished were in JavaScript.

eg. calling the in-built substr() function would look something like myVar.substr(x, y) but if you wrote your own version (may be function substr2(str, x, y)) you'll have to call it as
 

Not so elegant is it? 

JavaScript trim() function

Well, here is a way you could BIND your functions to the data type and call them like in-built functions… here's how: 

Trim function, trims all leading and trailing spaces: 

JavaScript startsWith() function

startsWith to check if a string starts with a particular character sequecnce: 

JavaScript endsWith() function

endsWith to check if a string ends with a particular character sequecnce:

All these functions once loaded will behave as built-in JavaScript functions.

Here are few examples:

Pretty slick huh.

JavaScript substring() Method

JavaScript substring is used to take a part of a string. The syntax of JavaScript substring method is given below:

stringObjectToTakeAPartOf.substring(start-index,stop-index)

• start-index: (Required - Numeric Value) - where to start the extraction
• stop-index: (Optional - Numeric Value) - where to stop the extraction

Notes about Javascript substring:

• If start-index is equal to stop-index, JavaScript substring returns an empty string.
• If stop-index parameter is omitted, JavaScript substring extracts characters from start-index to the end of the string.
• If parameters are 0or NaN, the parameters are threated as 0.
• If parameters are greater than the string's length, the parameters qill use string's length.
• If start-index > stop-index, then the JavaScript substring function swaps 2 parameters.

substring Example:

<script type="text/javascript">

var str = "Hello World";
document.write(str.substring(4,8));

</script>

The output of the above code is:

o wo

JavaScript substr() Method

The JavaScript substr() method works slightly different. Instead of the second parameter being an index number, it gives the number of characters. The syntax of JavaScript substr() is given below:

stringObjectToTakeAPartOf.substr(start-index,length)

• start-index: (Required - Numeric Value) - where to start the extraction
• length: (Optional - Numeric Value) - how many characters to extract

Notes about substr:

• To extract characters from the end of the string, use a negative start-index. (Internet Explorer returns the whole string which is wrong.)
• If the length parameter is omitted, JavaScript substr method extracts to the end of the string.
• substr() is not supported by Netscape 2, Netscape 3, Internet Explorer 3 and Opera 3.

JavaScript substr Example:

<script type="text/javascript">

var str = "Hello World";
document.write(str.substr(4,4));

</script>

The output of the above code is:

o wo

Since JavaScript substr() is not cross-browser, I never use it.