insert html into body javascript code example

Example 1: add element to body javascript

var elem = document.createElement('div');
elem.style.cssText = 'position:absolute;width:100%;height:100%;opacity:0.3;z-index:100;background:#000';
document.body.appendChild(elem);

Example 2: javascript add text to li

let arr = ["g", "o", "o", "g", "L", "e";
let ul = document.getElementById("id_ul");
let i =0;
arr.map(arr=>{
 var li = document.createElement("li");
 ul.appendChild(li);
 li.innerHTML = arr[i];
})