Delay and loop function call with setTimeout and setInterval in JavaScript

Both setTimeout() and setInterval() methods provide us a good way to control when to call a function when writing in JavaScript.

setTimeout()

The method calls a function or evaluates an expression after a specified number of milliseconds.

setTimeout( function(){ lookup(); }, 5000 );

function lookup(){
	$.ajax({
       url: 'notification/lookup',       
       type: 'GET',
       dataType: 'json',
       error: function() {
          
       },
       success: function(result) { 
       }
   });
}

Note: To prevent the function from running we use the clearTimeout() method.

setInterval()

The method calls a function or evaluates an expression at specified intervals in milliseconds.

setInterval( function(){ lookup_period(); }, 10000 );

function lookup_period(){
	$.ajax({
       url: 'notification/lookup_period',       
       type: 'GET',
       dataType: 'json',
       success: function(result) { 
       	if (result.success){
       		//do something
       	}
       }
   });
}

Note: The clearInterval() method is used to stop setInterval() from continuously running.

var i = 0;
intervalId = setInterval( function(){
	console.log('testing: ' + i); 		
	i++;
	if (i > 100){
		clearInterval(intervalId);	
	}			
}, 3000 );