Execution Context

Introduction

• When running a script, new execution context will be put into call stack

• To define an environment that the code is executed

Scenario

let x = 10;

function timesTen(a){
    return a * 10;
}

let y = timesTen(x);

console.log(y); // 100

Global Execution Context

Creation Phase

• Create the The Variable Object (VO) which is an object-like container created within an Execution Context

• For each variable declared with the var keyword, a property is added to VO that points to that variable and is set to 'undefined' (Hoisting)

• Create this : window

• Setup a memory heap for storing variables and function references

Execution Phase

• Execute functions line by line and create function execution context for each

• Assign variables with value

Function Execution Context

Creation Phase

Create the argument object which refer to the param of function

• Initialize the variable and param as undefined

• Create this: window

Execution Phase

• Execute the code one by one

• Assign the value declared in the function

References