How can I add or update a query string parameter?

Question

With javascript how can I add a query string parameter to the url if not present or if it present, update the current value? I am using jquery for my client side development

Answer 1

Here's an alternative method using the inbuilt properties of the anchor HTML element:

• Handles multi-valued parameters.
• No risk of modifying the # fragment, or anything other than the query string itself.
• May be a little easier to read? But it is longer.

    var a = document.createElement('a'),

	getHrefWithUpdatedQueryString = function(param, value) {
	    return updatedQueryString(window.location.href, param, value);
	},

	updatedQueryString = function(url, param, value) {
	    /*
	     A function which modifies the query string 
             by setting one parameter to a single value.

	     Any other instances of parameter will be removed/replaced.
	     */
	    var fragment = encodeURIComponent(param) + 
                           '=' + encodeURIComponent(value);

	    a.href = url;

	    if (a.search.length === 0) {
		a.search = '?' + fragment;
	    } else {
		var didReplace = false,
		    // Remove leading '?'
		    parts = a.search.substring(1)
		// Break into pieces
			.split('&'),

		    reassemble = [],
		    len = parts.length;

		for (var i = 0; i < len; i++) {
		    
		    var pieces = parts[i].split('=');
		    if (pieces[0] === param) {
			if (!didReplace) {
			    reassemble.push('&' + fragment);
			    didReplace = true;
			}
		    } else {
			reassemble.push(parts[i]);
		    }
		}

		if (!didReplace) {
		    reassemble.push('&' + fragment);
		}

		a.search = reassemble.join('&');
	    }

	    return a.href;
	};