Is JavaScript “not a function” compared to the “expected function”?

Question

In current Chrome, if I do this:

var i = 'foo'; i(); 

I get the error 'string is not a function' . I get similar errors if i is a number, undefined, etc.

However, from some real, more complex code, sometimes I see another error:

' expected function : function () {}'

I am trying to figure out how these two errors differ, or, to look at it differently, how to write minimal code that will throw an “expected function” error.

I tried messing around with callbacks and calling / applying, but none of them run this. Can someone explain how to reproduce this error?

Answer 1

The error message specification is missing. Therefore, each supplier implements it independently. The only way to unify this is to check yourslef data and throw the errors you expect.

 var i = 'foo'; if (!$.isFunction(i)){ throw 'expected function: function(){}'; }