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@dipakkr

dipakkr/block1.const Secret

Created Oct 21, 2020
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a = 10;
function add(x, y){
const result = x + y;
return result;
}
const name = 'github';
const final = add(10, 20);
```
As soon as you run this program, it creates a `Global Execution Content`, the place where the javascript thread will run line by line and run your code.
> You can think of `Global execution context` as an environment where the code runs.
> There can be multiple `execution context` in a program but a single `Global execution context`.
Now let's go back to the above code snippet and see what the JS engine does when we run the code.
- JS Engine parses your code line by line & identifies variables & functions created by code (which will be used in the execution phase)
- JS Engine setup memory space for variables & functions ( called as **Hoisting**)
**Hoisting ** is basically the JS Engine set-asides memory space for variables and functions used inside the code before your code is executed. These variables & functions comprise the Execution Context of any function that is being executed.
- A new Execution Context is created whenever function invocation is called.
> All variables in JS are initially set to `undefined`.
![Alt Text](https://dev-to-uploads.s3.amazonaws.com/i/mn2unuwm2ubk5oj56ky0.png)
Let's take one more example.
```
function y(){
const p = 100;
}
function x(){
y();
const t = 10;
}
x();
const r = 20;
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