Modal popup basic structure

WDS_modal.js

const WDS_modal = {
    lifeHour: 1,
    mSecondAnHour: 3600000,
    mSecondToNow: new Date().getTime(),
    expDateTime (){return this.mSecondToNow + (this.lifeHour * this.mSecondAnHour)},
    createModal(modalData){
        const backDrop = document.createElement('div');
        const modal = document.createElement('div');
        const modalClosingButton = document.createElement('span');
        backDrop.id = "modal_"+ modalData.content_id.toString();
        backDrop.style.cssText = "width:100%; height:100%; overflow:hidden; position: fixed; z-index: 100;left:0;top:0; background-color: rgba(0,0,0,0.5);";
        backDrop.innerHTML='';
        document.body.append(backDrop);
        modal.style.cssText = `width:${modalData.width}; height: ${modalData.height}; position:relative; margin: 200px auto; background-color:white; z-index: 101; border-radius: 3px; padding:10px; background-color: white;border: 1px solid #ccc; box-shadow: 1px 1px 1px black; box-sizing: border-box;`;

        modalClosingButton.innerHTML = modalData.closing_button_content;
        modalClosingButton.style.cssText="position: absolute; float:right; z-index:1002; cursor:pointer; top:5px; right:5px; padding:8px; cursor:pointer";
        backDrop.append(modal);

        modal.innerHTML = modalData.content;
        modal.append(modalClosingButton);
        modalClosingButton.addEventListener('click',()=>{
            this.closeModal(backDrop.id);
        })
        modal.addEventListener('click', (e)=>{
            e.stopPropagation();
        })
        backDrop.addEventListener('click', ()=>{this.closeModal(backDrop.id)});
    },
    closeModal(backDropID){
        console.log(backDropID);
        window.localStorage.setItem(backDropID,this.expDateTime());
        document.querySelector('#'+backDropID).style.display='none';
    },
    firstLoad(){
        let result = fetch('http://login.wdc.studio/gecici/banner_test_3.php').then(response=>response.json()).then(data=>{
            let modalRegisteredDateTime = window.localStorage.getItem("modal_"+data.content_id);
            let expired=true;
            window.localStorage.removeItem("modal_"+data.content_id)
            if(modalRegisteredDateTime){
                expired = parseInt(WDS_modal.mSecondToNow)-parseInt(modalRegisteredDateTime)>0
            }
            console.log(`
            Registered Exp Date: ${modalRegisteredDateTime}
            Current Date       : ${WDS_modal.mSecondToNow}
            Kalan sure: ${Math.abs((WDS_modal.mSecondToNow-modalRegisteredDateTime)/WDS_modal.mSecondAnHour)} saat
            Data.show:${data.show}
            Expired: ${expired}
            Gosterilsin mi: ${(data.show && expired)}
            `)
            if(data.show && expired){
                WDS_modal.createModal(data);
            }else{
                return false;
            }
        })
    }
}


window.addEventListener('load',WDS_modal.firstLoad);