Loop is more important than rest?

Question

I want to execute simple code when user click on my button:

1. First: change my cursor to \'wait\'
2. Next: execute loop
3. When loop is finished: cha

Answer 1

You are performing a blocking operation. This will certainly cause slow script warnings at some point. You can solve this by making the loop asynchronous:

var progress = document.getElementById('progress');

document.getElementById('gogogo').onclick = (function(){
    document.body.style.cursor = 'wait';

    var index = 0,
        updater;

    updater = function() {
        progress.textContent = index++;

        if (index < 30000) {
            setTimeout(updater, 50);
        } else {
            document.body.style.cursor = 'default';           
        }
    };

    updater();
});