How to unset a JavaScript variable?

To unset a variable in JavaScript, use the undefined. After that, use delete operator to completely remove it.

Let’s try the code snippet again.

var str = “Demo Text”;
window.onscroll = function() {
   var y = this.pageYOffset;
   if(y > 200) {
      document.write(nxt);
      nxt = undefined; // unset
     delete(nxt); // this removes the variable completely
     document.write(nxt); // the result will be undefined
   }
}