Why does the following work:
function sum(a,b) { return a + b; }
var result = sum.call(null,3,4); // 7
Why is result defined? I am invoking sum as a method of null. But null is not an object and cannot have properties!
What is going on?
The first argument for Function.prototype.call
is the context, which defines the this
value for the execution context of the invoked function, nothing else.
So basically, you're saying that this
is referring to null
(at least, in ES5 strict mode), but since you don't access this
anyway, it makes no difference.
In non-strict mode, this
cannot be null
, so it's replaced with the global object instead.