javascript regex to replace a substring

Question

In javascript, how would I use a regular expression to replace everything to the right of "Source="

Assume, for example:

var inStr="http://acme.com/mainpage.aspx?ID=25&Source=http://acme.com/fruitPage.aspx"
var newSoruceValue="http://acme.com/vegiePage.aspx"

Goal is to get this value in outStr:

var outStr="http://acme.com/mainpage.aspx?ID=25&Source=http://acme.com/vegiePage.aspx"

Thanks!!

epascarello · Accepted Answer · 2011-09-08 13:27:35Z

2

Assumes that source= will always be at the end

var inStr="http://acme.com/mainpage.aspx?ID=25&Source=http://acme.com/fruitPage.aspx"
var newSourceValue="http://acme.com/vegiePage.aspx"
var outStr = inStr.replace( /(Source=).*/, "$1" + newSourceValue);

answered Sep 8, 2011 at 13:27

epascarello

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4 Comments

user815460 Over a year ago

Thank you, works perfectly, if you have the time, I'd be grateful if you could briefly explain how it works. Thanks for the solution.

epascarello Over a year ago

Basic regular expression. The () is a capture group so it remembers what it matches. It is read with $1 since it is the first capture group. . means any character and * says to match one or more times.

user815460 Over a year ago

So, the replace method has 2 parameters, and the text that matches the pattern in the first parameter will be replaced with the resolved value of the second parameter. The () does not affect the pattern matching, it just remembers what it matches for later use with the $1.

epascarello Over a year ago

correct Documentation on replace() and reg exp

rapidfyre · Accepted Answer · 2011-09-08 13:31:15Z

0

Is "Source" always linked to the first occurrance of "&"? You could use

indexOf("&") + 7

(number of letters in the word "Source" + one for "=").

Then create the new string by appending the new source to the substring using the index from before.

answered Sep 8, 2011 at 13:31

rapidfyre

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Comments

Artem O. · Accepted Answer · 2011-09-08 13:48:36Z

0

string.replace( /pattern/, replace_text );

var outStr = inStr.replace( /&Source=.*$/, "&Source=" + newSoruceValue );

or

var outStr = inStr.replace( /(&Source=).*$/, "$1" + newSoruceValue )

edited Sep 8, 2011 at 13:48

answered Sep 8, 2011 at 13:29

Artem O.

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2 Comments

epascarello Over a year ago

Why the capture group around the part you are throwing away?

Artem O. Over a year ago

Oh, sure. Capture group for right text after the &Source= doesn't needed

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