jquery-deparam.js

/*
  jQuery deparam is an extraction of the deparam method from Ben Alman's jQuery BBQ
  http://benalman.com/projects/jquery-bbq-plugin/
*/
(function ($) {
  $.deparam = function (params, coerce) {
    var obj = {},
        coerce_types = { 'true': !0, 'false': !1, 'null': null };
      
    // Iterate over all name=value pairs.
    $.each(params.replace(/\+/g, ' ').split('&'), function (j,v) {
      var param = v.split('='),
          key = decodeURIComponent(param[0]),
          val,
          cur = obj,
          i = 0,
            
          // If key is more complex than 'foo', like 'a[]' or 'a[b][c]', split it
          // into its component parts.
          keys = key.split(']['),
          keys_last = keys.length - 1;
        
      // If the first keys part contains [ and the last ends with ], then []
      // are correctly balanced.
      if (/\[/.test(keys[0]) && /\]$/.test(keys[keys_last])) {
        // Remove the trailing ] from the last keys part.
        keys[keys_last] = keys[keys_last].replace(/\]$/, '');
          
        // Split first keys part into two parts on the [ and add them back onto
        // the beginning of the keys array.
        keys = keys.shift().split('[').concat(keys);
          
        keys_last = keys.length - 1;
      } else {
        // Basic 'foo' style key.
        keys_last = 0;
      }
        
      // Are we dealing with a name=value pair, or just a name?
      if (param.length === 2) {
        val = decodeURIComponent(param[1]);
          
        // Coerce values.
        if (coerce) {
          val = val && !isNaN(val)              ? +val              // number
              : val === 'undefined'             ? undefined         // undefined
              : coerce_types[val] !== undefined ? coerce_types[val] // true, false, null
              : val;                                                // string
        }
          
        if ( keys_last ) {
          // Complex key, build deep object structure based on a few rules:
          // * The 'cur' pointer starts at the object top-level.
          // * [] = array push (n is set to array length), [n] = array if n is 
          //   numeric, otherwise object.
          // * If at the last keys part, set the value.
          // * For each keys part, if the current level is undefined create an
          //   object or array based on the type of the next keys part.
          // * Move the 'cur' pointer to the next level.
          // * Rinse & repeat.
          for (; i <= keys_last; i++) {
            key = keys[i] === '' ? cur.length : keys[i];
            cur = cur[key] = i < keys_last
              ? cur[key] || (keys[i+1] && isNaN(keys[i+1]) ? {} : [])
              : val;
          }
            
        } else {
          // Simple key, even simpler rules, since only scalars and shallow
          // arrays are allowed.
            
          if ($.isArray(obj[key])) {
            // val is already an array, so push on the next value.
            obj[key].push( val );
              
          } else if (obj[key] !== undefined) {
            // val isn't an array, but since a second value has been specified,
            // convert val into an array.
            obj[key] = [obj[key], val];
              
          } else {
            // val is a scalar.
            obj[key] = val;
          }
        }
          
      } else if (key) {
        // No value was defined, so set something meaningful.
        obj[key] = coerce
          ? undefined
          : '';
      }
    });
      
    return obj;
  };
})(jQuery);