Change Parameters by Javascript Regex

Question

I have a string that contains URL like parameters:

var params="f5=212&f1=255&f3=400&f6=789&f9=243"

I want to change the value of f1, say from 255 to 355.

But the problem is parameters are dynamic and location of individual parameter changes. Below are possible cases:

var params="f1=456&f5=212&f3=400&f6=789&f9=243"
var params="f5=212&f1=451&f3=400&f6=789&f9=243"
var params="f5=212&f3=400&f1=255&f6=789&f9=243"
var params="f5=212&f3=400&f6=789&f9=243&f1=123"

How can I create the regex to change f1 value correctly by JavaScript?

possible duplicate of [Parse query string in JavaScript](http://stackoverflow.com/questions/2090551/parse-query-string-in-javascript) — All Workers Are Essential, May 25 '15 at 14:26

Casimir et Hippolyte · Accepted Answer · 2015-05-25T13:37:00.443

4

You can capture what is immediately before f1:

params = params.replace(/(^|&)f1=[^&]*/, '$1f1=355');

edited May 25 '15 at 13:37

answered May 25 '15 at 13:23

Casimir et Hippolyte

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Judging from the sample cases capturing what's before f1 doesn't seem necessary (but won't hurt of course). – Peter Herdenborg May 25 '15 at 13:29
Looks great Casimir. But would you mind sharing the code for replacing the any value that f1 has? It would be great if it is not looking for only integers. I will accept your answer then. – Jessie May 25 '15 at 13:31
With the above information added I take my comment back, obviously. – Peter Herdenborg May 25 '15 at 13:36
@Jessie: udapted for any kind of value *(`[^&]` all that is not a `&`)* – Casimir et Hippolyte May 25 '15 at 13:37
Wonderful. Thank you very much Casimir. – Jessie May 25 '15 at 13:40

score 0 · Answer 2 · answered May 25 '15 at 13:25

0

You can use this regex:

var new_var = 355;
params = params.replace(/f1=[0-9]{3}/,'f1='+new_var);

answered May 25 '15 at 13:25

n-dru

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Change Parameters by Javascript Regex

2 Answers2