Modal display on load with Local Storage

//
//  Video Modal
//

function setWithExpiry(key, value, ttl) {
    const now = new Date()
    // item is an object which contains the original value
    // as well as the time when it's supposed to expire
    const item = {
        value: value,
        expiry: now.getTime() + ttl
    }
    localStorage.setItem(key, JSON.stringify(item))
}

function getWithExpiry(key) {
    const itemStr = localStorage.getItem(key)
    // if the item doesn't exist, return null
    if (!itemStr) {
        return null
    }

    const item = JSON.parse(itemStr)
    const now = new Date()

    // compare the expiry time of the item with the current time
    if (now.getTime() > item.expiry) {
        // If the item is expired, delete the item from storage
        // and return null
        localStorage.removeItem(key)
        return null
    }
    return item.value
}

$(document).ready(function(){
    if (getWithExpiry('howtopopup') === null) {
        setTimeout(function(){
            $("#howtovideo").modal('show');
        }, 2000);
        setWithExpiry('howtopopup', true, 900000)
    }
});