Javascript Reg Expression to replace Get Parameter in the URL

Question

Using a regular expression, I want to write a function that will take a URL and a parameter name: ReplaceParamValueinURL (url, param, value).

If the parameter exists, it will replace the value in the URL.
If the parameter doesn't exist, it will add it to the URL along with the value.
If the parameter exists with no value, it will add the value to the parameter.

Is there an elegant way of doing all three in regex find and replace?

ReplaceParamValueinURL ("http://google.com?a=1&b=2&c=3, a , 4)
returns http://google.com?a=4&b=2&c=3 

ReplaceParamValueinURL ("http://google.com?a=1&b=2&c=3, a , 4)
returns http://google.com?a=4&b=2&c=3 

ReplaceParamValueinURL ("http://google.com?a=1&b=2&c=3, c , 4)
returns http://google.com?a=1&b=2&c=4 

ReplaceParamValueinURL ("http://google.com?a=1&b=2&c=3, d , 5)
returns http://google.com?a=1&b=2&c=3&d=5 

ReplaceParamValueinURL ("http://google.com?aaa=0&a=1&b=2&c=3, a , 6)
returns http://google.com?aaa=0&a=6&b=2&c=3 


ReplaceParamValueinURL ("http://google.com?a=1&b&c=3, b , 2)
returns http://google.com?a=1&b=2&c=3 

I am hoping to do this with Reg ex instead of split. I really appreciate it if you can explain your answer if the regex is too complex. Is there a jQuery function that already does this?

I guess it's a very common case but can have many corner cases.

ReplaceParamValueinURL ("http://google.com?a=1&b&c=3#test, a , 2)
returns http://google.com?a=2&b&c=3#test

mck89 · Accepted Answer · 2013-06-12 10:33:44Z

3

No you can't do it with a single regexp, but the function is pretty simple, i've tested it with all your examples so it should work:

function ReplaceParamValueinURL (url, name, val) {

    //Try to replace the parameter if it's present in the url
    var count = 0;
    url = url.replace(new RegExp("([\\?&]" + name + "=)[^&]+"), function (a, match) {
        count = 1;
        return match + val;
    });

    //If The parameter is not present in the url append it
    if (!count) {
        url += (url.indexOf("?") >=0 ? "&" : "?") + name + "=" + val;
    }

    return url;
}

answered Jun 12, 2013 at 10:33

mck89

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1 Comment

Faz Ya Over a year ago

Hi, I just realized this solution does not work with my real url localhost:8080/…

Shinov T · Accepted Answer · 2013-06-12 12:34:03Z

try this,

function ReplaceParamValueinURL(url , replceparam , replaceValue)
 {
  regExpression = "(\\?|&)"+replceparam+"(=).(&|)";
  var regExpS = new RegExp(regExpression, "gm");
  var getmatch = url.match(regExpS);
  var regExpSEq = new RegExp("=", "g");
  var getEqalpostion = regExpSEq.exec(getmatch);
  var newValue;
  if(getmatch[0].charAt(getmatch[0].length - 1) != "&")
    {
      var subSrtingToReplace  = getmatch[0].substring((getEqalpostion.index+ 1),getmatch[0].length );
      newValue =  getmatch[0].replace(subSrtingToReplace , replaceValue);
    }
  else
   {
      var subSrtingToReplace  = getmatch[0].substring((getEqalpostion.index+ 1) , getmatch[0].length - 1 );
      newValue =  getmatch[0].replace(subSrtingToReplace , replaceValue);
   }

 return  returnString = url.replace(regExpS , newValue);
}

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