how to check if jquery work code example

Example 1: check if jquery is loaded

$(document).ready(function(){
  if (jQuery) {  
    // jQuery is loaded  
    alert("Yeah!");
  } else {
    // jQuery is not loaded
    alert("Doesn't Work");
  }
});

Example 2: test if jquery works

/* Answer to: "test if jquery works" */

window.onload = function() {
    if (window.jQuery) {  
        // jQuery is loaded  
        console.log("jQuery has loaded!");
    } else {
        // jQuery is not loaded
        console.log("jQuery has not loaded!");
    }
}