Event loop

There are several internals inside javascript event loop:

• The call stack
• The Event Loop
• Macrotasks (Task Queue)
• Microtasks (Microtask Queue)

Call stack

The call stack is where JS tracks what function is currently executing. It is working as a stack way (Last in First out).

function greet() {
    console.log("Hello, world!");
}

function main() {
    greet();
}
main();

what javascript do is to push the functions into the stack and then execute them in order. And because javascript is a single-threaded language, only one thing is on the top of the stack at a time.

1. push main();
2. push greet();
3. push console.log

reference

• https://javascript.info/event-loop