Replace a querystring in url in javascript

Question

I have the following two urls:

url1 = http://localhost:8000/i/dashboard-view?
&level_to_load=1&click_value=%C2%AB%20backll%20Billing%20PartiesC2%
AB%20backll%20Billing%20Parties 

url2 = http://localhost:8000/i/dashboard-view?&level_to_load=1
&click_value=%C2%AB%20backll%20Billing%20PartiesC2%AB%20backll%20Billing%20Parties
&new_value=2

I want to be able to pull out the part that contains "click_value=...".

The resulting two urls after the regular expression should then be:

url1 = http://localhost:8000/i/dashboard-view?&level_to_load=1

url2 = http://localhost:8000/i/dashboard-view?&level_to_load=1&new_value=2

The current regex I have is:

url.replace(/click_value=.+&/, '');

But it is obviously insufficient. What would be the correct regex here?

zx81 · Accepted Answer · 2014-06-09 10:33:56Z

2

You can match the click_value GET strings with this regex:

&?click_value=[^&#\s]*

Therefore, to nix them,

result = url.replace(/&?click_value=[^&#\s]*/mg, "");

Discussion

The key here is matching the right number of characters and no more. I revised my original answer after @ridgerunner's insightful observation that in many urls, though maybe not in yours, there can be an anchor tag at the end, starting with #, which we don't want to replace. Thanks to him for the improved answer, which no longer uses lookaheads.

Token-by-Token

&?                       # '&' (optional (matching the most amount
                         # possible))
click_value=             # 'click_value='
[^&#\s]*                 # any character except: '&', '#', whitespace
                         # (\n, \r, \t, \f, and " ") (0 or more times
                         # (matching the most amount possible))

edited Jun 9, 2014 at 10:33

answered Jun 8, 2014 at 20:30

zx81

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8 Comments

ridgerunner Over a year ago

Note that the query portion of a URL may be followed by a: #fragment. Thus, instead of: .*?(?=&|$), (or better yet: .*?(?=[&#]|$) to handle any fragment), I'd just use: [^&#\s]* which is shorter, faster and pretty much matches the same thing.

zx81 Over a year ago

@ridgerunner Always a treat to read your regex thoughts... Always juicy... Hope you're traveling well. You are right about potential # fragments in urls. None in his input so I'll leave it as is, but added a segment pointing to an alternate solution in the comments. All the best. :)

pawel Over a year ago

Wouldn't /&?click_value=[^&]*/mg be good enough? If not, why?

zx81 Over a year ago

@pawel Because that also matches &click_value=34 and my brown dog :)

pawel Over a year ago

@zx81 just like the first example ;) (I was thinking about processing urls one by one). For urls in a blob of text I'd go with /&?click_value=[^&\s]*/mg : regex101.com/r/yT1pD9

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