<div class="left-menu">
@media screen and (max-width: 1000px) {
.left-menu{
display: none;
}
}
var leftMenu = document.querySelector(".left-menu");
console.log(leftMenu.style.display == 'none');
var leftMenu = document.querySelector(".left-menu");
var displayValue = window.getComputedStyle(leftMenu,null).getPropertyValue("display");
console.log(displayValue === 'none');