Question

In a web application that makes use of AJAX calls, I need to submit a request but add a parameter to the end of the URL, for example:

Original URL:

http://server/myapp.php?id=10

Resulting URL:

http://server/myapp.php?id=10&enabled=true

Looking for a JavaScript function which parses the URL looking at each parameter, then adds the new parameter or updates the value if one already exists.

Answer 1

A basic implementation which you’ll need to adapt would look something like this:

function insertParam(key, value) {     key = encodeURIComponent(key);     value = encodeURIComponent(value);      // kvp looks like ['key1=value1', 'key2=value2', ...]     var kvp = document.location.search.substr(1).split('&');     let i=0;      for(; i<kvp.length; i++){         if (kvp[i].startsWith(key + '=')) {             let pair = kvp[i].split('=');             pair[1] = value;             kvp[i] = pair.join('=');             break;         }     }      if(i >= kvp.length){         kvp[kvp.length] = [key,value].join('=');     }      // can return this or...     let params = kvp.join('&');      // reload page with new params     document.location.search = params; } 

This is approximately twice as fast as a regex or search based solution, but that depends completely on the length of the querystring and the index of any match

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the slow regex method I benchmarked against for completions sake (approx +150% slower)

function insertParam2(key,value) {     key = encodeURIComponent(key); value = encodeURIComponent(value);      var s = document.location.search;     var kvp = key+'='+value;      var r = new RegExp('(&|\\?)'+key+'=[^\&]*');      s = s.replace(r,'$1'+kvp);      if(!RegExp.$1) {s += (s.length>0 ? '&' : '?') + kvp;};      //again, do what you will here     document.location.search = s; }