jsFiddle

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• JavaScript
• Result

var log = $('log');
var count = 0;
var addDot = function(){
    if(count < 20){
        this.set('text', this.get('text') + '.');
        count++;
    } else {
        log.empty();
        count = 0;
    };
};

var myPeriodical = addDot.periodical(50, log);

(function(){ $clear(myPeriodical); }).delay(4000);