regular expression in Javascript

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programAngel

In code that I am reading I have the following regular expression:

'([0-9]*)x([0-9]*)'

and for the code:

"400x300"

It give me the following array:

[400x300,400,300]

I understand why the first element in the array, 400x300, but how come the last two match the regular expression?

They don't have the x.

Can someone please explain to me why the last 2 element match the regular expression.

iBeZi

The two areas enclosed in brackets tell the regular expression that you want to "capture" whatever appears inside the brackets.

So the regular expression matches "400x300" as a whole, but then gives you the two numbers separately because they are enclosed in brackets.

programAngel

iBeZi, thank you.

wbport

Putting parenthesis "()" around part of a regular expression is a way to determine it's value and take appropriate action. For example, in the text based music notation system abc, the following examines a note:

 //           <stc><-- accidental----><--note--><octav><num>< / ><dem><trail>
 var anote = /(\.?)(\^{0,2}|=?|_{0,2})([A-Ga-g])([',]*)(\d*)(\/*)(\d*)([- ]*)/;

Only the upper or lower case letters "a-g" have to be there-- a stacatto dot, an accidental, octave change, duration, and/or trailing dash or space are all optional. This is an example of some code that follows a match command:

     for (var i =0; i<result[4].length; i++) {
       var achar = result[4].charCodeAt(i); // alert("achar = " + achar);
       if (achar == 44) {pos -= 7;} // Comma down
	   if (achar == 39) {pos += 7;} }  //Apostrophe, up

HTH