javascript first loading page code example

Example 1: window.onload execute after load page

/* javascript function is executed after 5 seconds page was loaded */
window.onload = function() {
   setTimeout(loadAfterTime, 5000)
}; 
 
function loadAfterTime(){
   document.getElementById("menu").style.display="block";
}

Example 2: wait for page load js

window.addEventListener('load', function () {
  
})

//THE OTHER ANSWER IS WRONG (has a syntax error)