JavaScript: single-threaded and synchronous

A few days ago single threaded and synchronous were just 2 heavy words for me. If this is you right now, don't worry I'll try my best to make you understand.

So, let's get started:

Single-threaded and synchronous are not that much different.

Single-threaded: It can do only 1 thing at a time and has a single call stack (don't worry just read and soon you'll get what it is)

Synchronous: As the name suggests synchronous means to be in a sequence. So, basically a function has to wait for the earlier function to get executed and everything stops until the wait is over.

The call stack is basically a data structure that records where we are in the program. If we step into a function we push it to the top of the stack and when we return a value from the function we basically pop the function off from the stack.

Let's understand it by running the below code:

function multiply(a, b){
     return a*b;
}

function square(n){
     return multiply(n)
}

function printSquare(n){
     let squared = square(n)
     console.log(squared)
}

printSquare(4)        

👇See how the above code executes: There will be a main() function when the file starts executing then we call printSquare which gets pushed over the top of the stack which in turn calls a square function which gets pushed over at the top of the stack which in turn calls the multiply function which gets pushed over at the top of the stack.

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