What five JavaScript concepts do I need to understand to be a good AngularJS developer?

Question

Suppose I'm used to coding on the server side (with server-side languages), and now I'm learning AngularJS. That means I first need a good understanding of JavaScript.

If I don't have to time to fully learn JavaScript right now, what five JavaScript concepts would you recommend I learn first/well in order to be an effective AngularJS developer?

Answer 1

1. the type system: there are two fundamentally different kinds of values: primitives and objects. Number, string, boolean, null, undefined are all primitives.
   Array ( [1,2,3] ), object ( { prop1: value1, prop2: value2 } ), and function are all objects.
2. prototypal inheritance – this is especially important when you attempt to databind in AngularJS to a primitive
3. array['syntax'] === array.syntax; array['$id'] === array.$id; array[someExpression] has no eqivalent "." notation
4. variable scope and assignment
   • a variable defined anywhere inside a function is visible everywhere inside that function
   • when a variable is assigned an object, it is assigned a reference (not a copy). This becomes important in AngularJS when, e.g., you fetch JSON data from a server and you assign the results to a variable. This resets the reference. Other variables (say in your controller) that point to the old reference continue to point to the old reference. (example)
5. closures – these are very useful when defining AngularJS services (example) and when defining methods on a controller using this (example)

Also note that JavaScript is single-threaded!

Answer 2

In my view you should get clarity on the following topics

1) call by value vs call by reference in javascript

Reason: because in angularJS we deal with a lot of objects. You will be clear about their behaviour once you understand this

2) Scope chain and IIFE(Immediately invocable function expression)

Reason: When you work on an application using angularJS IIFEs play a major role in manipulating your scope.

3) Closures

Reason: One of the most important javascript concept. If you see source code of a lot of famous libraries and frameworks built on javascript, they have used closures a lot. Closures will also help you understand how factories work in depth.

4) Dependency Injection

Reason: A javascript concept on which Angular JS is based

5) You can also go through some good style guides for AngularJS. For instance you can refer to this one: https://github.com/johnpapa/angular-styleguide