playbackRate at Coursera

gistfile1.js

    /** function set_speed(speed)
      * Set the video speed
      *
      * @param double speed - target speed
      *
      * @return void
      */
    this.is_set_speed_enabled = function() {
        var featureExists = typeof(this.mediaelement_media) === 'object'
                && this.mediaelement_media !== null
                && typeof(this.mediaelement_media.playbackRate) === 'number'
                && this.mediaelement_media.playbackRate > 0;
        if (featureExists) {
            var userAgentWorks = !(mejs.MediaFeatures.isAndroid ||
                mejs.MediaFeatures.isBustedAndroid ||
                mejs.MediaFeatures.isiOS ||
                mejs.MediaFeatures.isiPad ||
                mejs.MediaFeatures.isiPhone);
            if (userAgentWorks) {
                return true;
            }
        }
        return false;
    }

    this.set_speed = function(speed) {
        var self = this;
        self.mediaelement_media.playbackRate = speed;
        // It only works in Safari and FF if we set it after the readyState > 0
        if (self.mediaelement_media.readyState === 0) {
            self.mediaelement_media.addEventListener('loadedmetadata', function() {
                self.mediaelement_media.playbackRate = speed;
            });
        }
    }

    this.get_speed = function(speed) {
        if(this.is_set_speed_enabled()) return this.mediaelement_media.playbackRate;
        else return 1;
    }