JS Set onClick action to a Button that was create inside a loop

How to define the onClick property of the Buttons created inside this loop?.JQuery doesn't seem to work at all for that class.

    for(started somewhrere...

        var button = document.createElement('button')
        var div = document.createElement('div')
        var img = document.createElement('img')
            img.src = "../img/download.png"
        var p = document.createElement('p')
            p.appendChild(document.createTextNode("Descargar"))

        div.appendChild(img);
        div.appendChild(p);
        button.appendChild(div);

        button.onClick = "DOSOMETHINGFFS()"

        button.className = "download"

     for end somewhere...}

function DOSOMETHINGFFS(){
    alert("no")
}

BTW JQuery isn't really helping at all

$(".download").click(function() {
    alert("ok")
});

Solution

Make sure you're actually adding the elements to the page (e.g. container.appendChild below), and you misspelled onclick. (You had a capital C.) Otherwise, I think what you did was okay, but it's better to assign the actual function instead of a string with JavaScript code that makes a function call:

function doSomething(url){
    console.log("download " + url);
}

var container = document.getElementById("container");
for (var i = 0; i < 5; i++) {
    var button = document.createElement('button');
    button.innerText = "click me";
    button.className = "download";
    button.onclick = (function (url) {
        return function () {
            doSomething(url);
        };
    })("URL #" + i);
    container.appendChild(button);
}

$('.download').click(function () {
    console.log("clicked from jQuery handler");
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="container"></div>

EDIT

Also used jQuery to add a handler. That works fine too.

EDIT 2

Changed the onclick example to include a different parameter for each button. There are several ways to achieve this, but I used an immediately-invoked function expression (IIFE).