Here is Pseudo-code of jQuery
$(document).ready(function(){
printHelloworld();
});
var printHelloworld = function(){
console.log('hello world');
}
In this sample, the console will print hello world.
My question is that Function expression must be assigned before usage, but in this sample, I used the printHelloworld() before assigned it. I do not know what have .ready() function done? Did it do something to hoist the function?
The var hoisted the printHelloworld function declaration to the top of the function (or script). It wasn't initialized until you assigned it after your $(document).ready() statement, but the anonymous function you passed to ready still held a reference to the variable. By the time the function executed, the printHelloworld variable was initialized and usable.
See: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/var
Because variable declarations (and declarations in general) are processed before any code is executed, declaring a variable anywhere in the code is equivalent to declaring it at the top. This also means that a variable can appear to be used before it's declared.
