Correctly Parse Query String

parse-query.js

function parseQuery(q) {
	var dec = window.decodeURIComponent;

	var hash = {};

	//if `q` is `null` or `undefined`, there are no keys
	if (q == null) {
		return hash;
	}

	//if the string starts with a `?` character, strip it off
	if (/^\?/.test(q)) {
		q = q.substr(1);
	}

	//if the string is empty, there are no keys
	if(q === ''){
		return hash;
	}

	//split the string on key-value pair separators
	//`&` and `;` are used to separate key-value pairs
	q = q.split(/[&;]/g);

	//iterate through each key-value pair
	for (i = 0; i < q.length; i += 1) {
		var key, value, data = q[i];

		//split the key-value pair on the first key-value separator
		//`=` is used to separate keys from values
		var index = data.indexOf('=');
		if (index < 0) {
			//if no `=` is present
			// - the entire key-value pair is used as the key
			// - the value is null
			key = dec(data);
			value = null;
		} else {
			//if `=` is present
			// - rawKey is the part of the string before the `=`
			// - rawValue is the part of the string after the `=`
			var rawKey = data.slice(0, index);
			var rawValue = data.slice(index + 1);
			key = dec(rawKey);
			value = dec(rawValue);
		}

		//check if the key is present in the hash
		if (hash.hasOwnProperty(key)) {
			//if it is, add the new value to the collection of values
			hash[key].push(value);
		} else {
			//if it isn't, create a new collection of values
			hash[key] = [value];
		}
	}

	return hash;
}

parse-query.min.js

function parseQuery(a){var b=window.decodeURIComponent,c={};if(null==a)return c;if(/^\?/.test(a)&&(a=a.substr(1)),""===a)return c;for(a=a.split(/[&;]/g),i=0;i<a.length;i+=1){var d,e,f=a[i],g=f.indexOf("=");if(g<0)d=b(f),e=null;else{var h=f.slice(0,g),j=f.slice(g+1);d=b(h),e=b(j)}c.hasOwnProperty(d)?c[d].push(e):c[d]=[e]}return c}

uniform.js

(function(win){
  var dec = win.decodeURIComponent;
  var parser = document.createElement('a');

  function Uniform(){}
  var u = Uniform.prototype = {};

  u.parseQuery = function(q) {
    var hash = {};
    var collector = {};

    //if `q` is `null` or `undefined`, there are no keys
    if (q == null) {
      return hash;
    }

    //if the string starts with a `?` character, strip it off
    if (/^\?/.test(q)) {
      q = q.substr(1);
    }

    //if the string is empty, there are no keys
    if(q === ''){
      return hash;
    }

    //split the string on key-value pair separators
    //`&` and `;` are used to separate key-value pairs
    q = q.split(/[&;]/g);

    //iterate through each key-value pair
    for (i = 0; i < q.length; i += 1) {
      var key, value, data = q[i];

      //split the key-value pair on the first key-value separator
      //`=` is used to separate keys from values
      var index = data.indexOf('=');
      if (index < 0) {
        //if no `=` is present
        // - the entire key-value pair is used as the key
        // - the value is null
        key = dec(data);
        value = null;
      } else {
        //if `=` is present
        // - rawKey is the part of the string before the `=`
        // - rawValue is the part of the string after the `=`
        var rawKey = data.slice(0, index);
        var rawValue = data.slice(index + 1);
        key = dec(rawKey);
        value = dec(rawValue);
      }

      (collector.hasOwnProperty(key)) ? collector.push(value) : (collector[key] = [value]);

      hash[key] = (hash.hasOwnProperty(key)) ? collector[key] : value;
    }

    return hash;
  };

  u.parse = function(url){
    parser.href = url;
    return parser;
  };

  u.new = function(opts){return new Uniform(opts)};

  win.uniform = new Uniform();
})(window)