var a = [4];
Object.prototype.toString(a); //-> [object Object]
Object.prototype.toString.call(a); //-> [object Array]
Why are the two different ? Can someone post a detailed explanation ?
Because according to ECMA-262, the following occurs when calling
Object.prototype.toString as a method:
| 15.2.4.2 Object.prototype.toString ( )
|
| When the toString method is called, the following steps are taken:
|
| 1. Get the [[Class]] property of this object.
| 2. Compute a string value by concatenating the three strings
"[object ", | Result(1), and "]".
| 3. Return Result(2).
So when processing:
Object.prototype.toString(a);
The this keyword is a reference to Object.prototpye, which is an
Object (its [[class]] is Object), so the result [object Object] will
result regardless of the argument provided (even none at all).
When you use:
Object.prototype.toString.call(a);
the call method sets toString's this keyword as a reference to a, an
Array, so you get [object Array].
Incidentally, this might be the ultimate "isArray" test as it provides
access to the internal [[class]] property.
