Check whether a URL variable is set using JQuery

Question

I would like to know whether there is a jQuery function which can check whether a variable in the URL is set.

Something similar to the isset() function in PHP

Thanks

Answer 1

jQuery doesn't have native functions to get URL parameters.

But you can write your own plugin to it:

$.extend({
  getUrlVars: function(){
    var vars = [], hash;
    var hashes = window.location.href.slice(window.location.href.indexOf('?') + 1).split('&');
    for(var i = 0; i < hashes.length; i++)
    {
      hash = hashes[i].split('=');
      vars.push(hash[0]);
      vars[hash[0]] = hash[1];
    }
    return vars;
  },
  getUrlVar: function(name){
    return $.getUrlVars()[name];
  }
});

Then you can do anything like it:

if ($.getUrlVar("MyParam") != null) {
    // Do anything...
}

Answer 2

jQuery does not provide such methods. But you don’t even need jQuery to do so:

(function() {
    var params = null;
    this.l = typeof Location !== "undefined" ? Location.prototype : window.location;
    this.l.getParameter = function(name) {
        return Array.prototype.slice.apply(this.getParameterValues(name))[0];
    };
    this.l.getParameterMap = function() {
        if (params === null) {
            params = {};
            this.search.substr(1).split("&").map(function(param) {
                if (param.length === 0) return;
                var parts = param.split("=", 2).map(decodeURIComponent);
                if (!params.hasOwnProperty(parts[0])) params[parts[0]] = [];
                params[parts[0]].push(parts.length == 2 ? parts[1] : null);
            });
        }
        return params;
    };
    this.l.getParameterNames = function() {
        var map = this.getParameterMap(), names = [];
        for (var name in map) {
            if (map.hasOwnProperty(name)) names.push(name);
        }
        return names;
    };
    this.l.getParameterValues = function(name) {
        return this.getParameterMap()[name];
    };
})();

This extends the location object with the methods getParameter, getParameterMap, getParameterNames, and getParameterValues (similar to Java’s ServeletRequest) that can be used as follows:

if (typeof location.getParameter("foo") !== "undefined") {
    // foo parameter exists
}

The return values of getParameter have the following meaning:

• undefined: given parameter not present
• null: given parameter has no assigned value (e.g. foo in a=b&foo&c=d)
• any string value otherwise.