Lessan Vaezi Lessan Vaezi - 1 year ago 85
Javascript Question

Adding a parameter to the URL with JavaScript

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:


Resulting URL:


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 Source

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

function insertParam(key, value)
    key = encodeURI(key); value = encodeURI(value);

    var kvp = document.location.search.substr(1).split('&');

    var i=kvp.length; var x; while(i--) 
        x = kvp[i].split('=');

        if (x[0]==key)
            x[1] = value;
            kvp[i] = x.join('=');

    if(i<0) {kvp[kvp.length] = [key,value].join('=');}

    //this will reload the page, it's likely better to store this until finished
    document.location.search = kvp.join('&'); 

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

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;
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