What is the code execution order in javascript?

Question

How exactly does the code execute in JavaScript? I mean, in what order? Will there be a difference in execution order if I declare a function like this:

function render() { // Code here } 

instead of this:

 var render = new function(){ // Same code here } 

Does JavaScript execute the functions defined in the script file, regardless of whether it is called by the event handler? (e.g. onload=function() ).

And finally, if a function is defined in another function, when the parent function is called, is the lower function also called? eg.

 function a(){ function b(){ // code } function c(){ //code } } 

I am trying to get a concrete idea of ​​the execution order in JavaScript.

Answer 1

 var render = new function(){ // same code here } 

The new keyword does not create a new function. It creates a new object by running the function. Thus, this would actually fire up the body of the method and return the object.

If your requestor, when functions are parsed and added to the scope, then this implementation is specific, but all functions go up at the top of the scope and are usually analyzed before any code is executed.

Functions are only executed when you call them by calling f()

Answer 2

A function declaration is declared (therefore, it can be called earlier in the code, then it is defined), the function operator is not.

Does JavaScript execute the functions defined in the script file, regardless of whether they are called by the event handler?

The function is called when it is called. Either because something has theFunction followed by () (possibly with arguments), or because it is made by an event handler.

onload="function"

If it's JS, then it assigns a string to something waiting for the function. If this is HTML, you need to () call the function.

And finally, if a function is defined in another function, when the parent function is called, is the lower function also called?

Not. A function is called only when it is called. Declaring a function inside another limits the scope.

Answer 3

When you declare a function, it is not executed until it is called (this is true for those that were declared in onload and other events).

For nested functions, they are not executed automatically when the top-level function is called UNTIL, the calling function calls them.