Remove childElements one-by-one in pure JavaScript

Question

I have:

<div id="alerts">
    <div class="alert">alert 1</div>
    <div class="alert">alert 2</div>
</div>

and want to remove these alerts one-by-one after 4000 ms by an interval of 500 ms in pure JavaScript .

I have this:

window.onload = function(){
    alerts = document.getElementById( 'alerts' );
    if( alerts ){
        alert = alerts.getElementsByClassName( 'alert' );
        setTimeout( function(){
            for( var i=0; i < alert.length; i++ ){
                ( function( i ){
                    setTimeout( function(){
                        alerts.removeChild( alert[i] );
                    }, 500);
                }
                )(i);
            }
        }, 4000);
    }
}

I think this is not the right way of using setTimeout .

Answer 1

The getElementsByClassName returns a live collection which means when a selected element is removed or changed in the dom the referred collection also changes.

So in your example when you start the alert has 2 elemnets, but when the first element is removed then alert will have only 1 element but you are referring to alert[1] which will be undefined.

So the solution will be is to remove the first element from the array.

 window.onload = function() { var alerts = document.getElementById('alerts'); if (alerts) { alert = alerts.getElementsByClassName('alert'); setTimeout(function() { for (var i = 0; i < alert.length; i++) { (function(i) { setTimeout(function() { alerts.removeChild(alert[0]); }, i * 500); //need increasing timeouts })(i); } }, 4000); } } 

 <div id="alerts"> <div class="alert">alert 1</div> <div class="alert">alert 2</div> </div> 

---

But you can use setInterval() to solve this in a better way like

 window.onload = function() { var alerts = document.getElementById('alerts'); if (alerts) { var alert = alerts.getElementsByClassName('alert'); setTimeout(function() { var interval = setInterval(function() { alerts.removeChild(alert[0]); if (!alert.length) { clearInterval(interval) } }, 1000); }, 3000); } } 

 <div id="alerts"> <div class="alert">alert 1</div> <div class="alert">alert 2</div> </div> 

Answer 2

A simpler approach would be to use setInterval

 window.onload = function() { alerts = document.getElementById('alerts'); if (alerts) { alert = alerts.getElementsByClassName('alert'); var interval = setInterval(function() { if (alert.length) { alerts.removeChild(alert[alert.length - 1]); } else { clearInterval(interval); } }, 4000); } } 

 <div id="alerts"> <div class="alert">alert 1</div> <div class="alert">alert 2</div> </div>