summary of Intermediate Javascript Concepts

In this session, you learned about the following concepts:

• There are two types in which the variables can be passed - by value and by reference. All the primitive types are passed by value and all the non-primitive types are passed by reference.
• The .__proto__ property of a variable refers to either an object or to null. Remember that you can implement inheritance in JavaScript by assigning the prototype of an object to another object.

• There are two kinds of scope in JavaScript:

  • Local Scope - Anything inside a function is in its local scope.

  • Global Scope - Anything not inside any function is in its global scope.

• A closure is basically an inner function that has access to the outer (enclosing) function’s resources due to the scope chain where a child can access all the resources of its parent.

• All the variables which are declared in your code are moved at the top and remembered by the compiler. This is the concept of hoisting.

• The popular ‘this’ keyword points to the global window object in the context of browsers when written inside a regular function call. However, in the case of a method, which is defined as a function inside an object, the ‘this’ keyword points to the object to which the method is bond.

• The methods - bind(), call() and apply() are used to bind a function while passing the desired scope to the inner function. This is also useful to solve the problem of 'this' keyword pointing to the global object inside a function in an object.