Difference in Jquery.each() and Array.prototype.forEach() method

• Placement of arguments in the callback.

• Quantity of arguments in the callback (The .forEach() gives you get a reference to the original collection.)

• Default this value in the callback. (In jQuery it's the current item, in .forEach() it's the JavaScript default)

• Ability to manually set the this value in the callback. (jQuery doesn't give this option, .forEach() lets you via a third argument.)

• Avoidance of non-defined properties on sparse Arrays. (The .forEach() avoids them, jQuery includes them.)

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They're very differently behaving methods. jQuery's doesn't make any attempt to be compliant with or complimentary of the standard behaviors.

In addition to Crazy Train's answer:

What i wan to know is ,do jquery.each() invokes function for object without length property??

Read the source:

// args is for internal usage only
each: function( object, callback, args ) {
  var name, i = 0,
      length = object.length,
      isObj = length === undefined || jQuery.isFunction( object );

  if ( args ) {
    ...

  // A special, fast, case for the most common use of each
  } else {

    if ( isObj ) {
      for ( name in object ) {
      }
      ...
    }
  }
  return object;
},

So you can see if there is no length property, or it has the value undefined, then jQuery thinks it's a plain object and will do a for..in loop over the enumerable properties with no guard against inherited properties.