Javascript Regex replace by group

Question

Suppose you have this string: url?param1=something&param2=something&param3=something which can also be only url?param1=something.

How would you do to convert param1=something to param1=anotherthing ?

I am able to do it this way:

var regex = /param1=.*(&|$)/;
var string = 'url?param1=something&param2=something&param3=something';
var newValue = 'anotherthing';
string.replace(regex, 'param1='+newValue);

However, I do not like the fact of repeating all the search term, so I'm asking if it is possible to group the needed pattern to replace, in this case would be .* and replace only that.

For example, saying that $1 belongs to group 1. This is fictitious.

var regex = /param1=(.*)(&|$)/;
var string = 'url?param1=something&param2=something&param3=something';
var newValue = 'anotherthing';
string.replace(regex, $1, newValue);

Bilal · Accepted Answer · 2014-03-31 12:56:15Z

2

Try this:

var string = 'url?param1=something&param2=something&param3=something';
alert(string.replace(/(param1)([^&]+)/, '$1=newparam1'));

if you want to set multiple parameters to the same value

alert(string.replace(/(param1|param2)([^&]+)/g, '$1=newparam'));

answered Mar 31, 2014 at 12:56

Bilal

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Comments

epascarello · Accepted Answer · 2014-03-31 14:37:47Z

0

Add another capture group...

var regex = /(param1=)([^&]*)/;
var string = 'url?param1=something&param2=something&param3=something';
var newValue = 'anotherthing';
string.replace(regex, "$1" + newValue);

edited Mar 31, 2014 at 14:37

answered Mar 31, 2014 at 12:51

epascarello

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2 Comments

JorgeeFG Over a year ago

Hey thanks, your example gives me "url?param1=anotherthing" instead of the full url, any tip?

epascarello Over a year ago

Whoops, I did not pay attention to your reg exp, it should have been /(param1=)([^&]*)/;

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