Javascript foo.call (object) vs. object.foo ()

Question

I looked at the jQuery source code and then saw that instead of context.foo() they use foo.call(context) .
for example, if this is the array they use:

 return slice.call( this ); 

instead:

 return this.slice(); 

what's the difference, and does he prefer (in terms of performance) to make these calls?

Answer 1

The problem is that “foo” cannot actually be a “context”. In this case, the only real choice is to use .call() (or .apply() , if necessary).

If you have an object with the property “foo”, that function, then there is no real reason to use .call() .

Answer 2

In addition to @Pointy's answer, directly calling a member function seems a lot faster than Class.prototype.foo:

http://jsperf.com/javascript-foo-call-object-vs-object-foo