javascript，无法覆盖功能

Question

how can I override function length in other file js ?

  jQuery(function ($) {    

    $.fn.normal_text = function (text) {

           $.fn.normal_text.length = function(){
              ...
           }

        }

}

I try this:

$(document).ready(function(){
    $.fn.normal_text.length = function(){ alert('123'); }
});

But it not work.I seem to be crazy with it

Answer 1

You can't override the length property on functions because it is a read-only builtin.

Under "Properties of function instances" in the language specification:

15.3.5.1 length

The value of the length property is an integer that indicates the “typical” number of arguments expected by the function. However, the language permits the function to be invoked with some other number of arguments. The behaviour of a function when invoked on a number of arguments other than the number specified by its length property depends on the function. This property has the attributes { [[Writable]]: false , [[Enumerable]]: false, [[Configurable]]: false } .

The bold part explains that the length property on function instances is not writable.

Answer 2

normal_text是一个函数，而不是一个对象，所以你不能覆盖它的属性。