Creating a top banner box

WDS_topBanner.js

const WDC_banner ={
    lifeHour: 1,
    mSecondAnHour: 3600000,
    mSecondToNow: new Date().getTime(),
    expDateTime (){return this.mSecondToNow + (this.lifeHour * this.mSecondAnHour)},
    placeTheBanner(bannerData){
        const bannerClosingButton = document.createElement('span');
        const topBanner = document.createElement('div');
        topBanner.innerHTML= bannerData.content;
        topBanner.id= "banner_"+ bannerData.content_id.toString();
        topBanner.style.position='inline';
        topBanner.style.overflow='hidden';
        topBanner.style.height=bannerData.height;
        topBanner.style.width=bannerData.width;
        topBanner.style.height=bannerData.height+'px';
        bannerClosingButton.innerHTML = bannerData.closing_button_content;
        bannerClosingButton.style.position='absolute';
        bannerClosingButton.style.zIndex=1;
        bannerClosingButton.style.cursor='pointer';
        bannerClosingButton.style.top='5px';
        bannerClosingButton.style.right='5px';
        bannerClosingButton.style.padding='8px';
        topBanner.append(bannerClosingButton);
        bannerClosingButton.addEventListener('click',()=>{
            this.animateAndClose(topBanner.id)
        })
        document.body.insertAdjacentElement('afterbegin', topBanner);
    },
    animateAndClose(topBannerID){
        let topBanner = document.querySelector('#'+topBannerID);
        let animate = window.setInterval(
            ()=>{
                if(parseInt(topBanner.style.height)<3){
                    console.log(this.expDateTime())
                    window.localStorage.setItem(topBannerID,this.expDateTime());
                    topBanner.style.display='none';
                    clearInterval(animate);
                }
                topBanner.style.height = (parseInt(topBanner.style.height)-3)+'px';
            },
            20)
    },
    firstLoad(){
        let result = fetch('http://login.wdc.studio/gecici/banner_test_3.php').then(response=>response.json()).then(data=>{
            let bannerRegisteredDateTime = window.localStorage.getItem("banner_"+data.content_id);
            let expired=true;
            if(bannerRegisteredDateTime){
                expired = parseInt(WDC_banner.mSecondToNow)-parseInt(bannerRegisteredDateTime)>0
            }
            if(data.show && expired){
                WDC_banner.placeTheBanner(data);
            }else{
                return false;
            }
        })
    }
}
window.addEventListener('load', WDC_banner.firstLoad)