Doubt about functions in Javascript lines

Question

I have a question about how functions work in Javascript, was looking at some examples and does not follow logic like other programming languages (PHP and Lua). I can create a Function on line 99 and call it on line 1 which will apparently work.

Take an example:

var exemplo = document.getElementByID('exemplo'),
    exemploDois = document.getElementByID('exemplo2');

    init();

    function init(){
        // ... function
    }

This in other languages would generate an error by returning a nil value. In Javascript do you not need to follow the function before calling it? This makes me a little confused when creating new JS codes.

In other languages the correct and the following:

var exemplo = document.getElementByID('exemplo'),
    exemploDois = document.getElementByID('exemplo2');

    function init(){
        // ... function
    }

    init();

Can the same be done in variables? So you understand the javascript does not need to follow guiding the functions before in the code.