1510-function-cfus.md

JavaScript Functions

I can explain the difference between function declarations and function expressions.

• function expressions are defined by var name = ... are invoked with name(...) but are not hoisted.
• function declarations are defined by function name(...){...}, are invoked similarly, and are hoisted.

Rules for this:

• 1. this is the global object (window, or global when in terminal)
• 2. this is whatever object the function/method is being called from
• 3. this is whatever you say this is.

I can explain what the value of this is in a normal function.

• this is the window itself.

I can explain what the value of this is when called from the context of an object.

• this is the object.

I can explain how to explicitly set the value of this in a function.

• the call method executes a function, but the first parameter is the new this.

I can explain the difference between call and apply.

• the apply method and call method are identical, except, call takes 2nd - nth parameter as parameters, while call takes these parameters as an array.
• note... in ruby you can use splat for this kind of thing. arry = [1,2,3], def method(x,y,z) x + y + z end, method(*arry) works. In ES6, method(...arry) also works.

I can describe an case where I might need to use bind to avoid polluting the global scope.

I can explain how bind works.

• calling bind on a function returns a brand new function, where the first param to bind sets this in new function, the latter params do partial function application.