how I'd make a

content.scss

@keyframes content-peep{
    //bounce frames
}

.content{
    margin-top: 100vh;
    
    &-is_peeping{
        animation: content-peep 200ms 1 500ms;
    }
}

hero-slider.js

function HeroSlider(){
    
}

HeroSlider.prototype.windowPeep = function(){
    $(body).addClass('content-is_peeping');
}

HeroSlider.prototype.init = function(){
    $(window).on('focus', $.proxy(this.windowPeep, this));
}

var slider = new HeroSlider();

$(function(){
    slider.init();
});