JavaScript fabonacci series with number of elements by input number

In Fibonacci series of numbers, each number is the sum of the two preceding ones.

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377

Fn = F(n-1) + F(n-2)

Enter Number of elements of the series.

Output here

<html>
<head>
<title></title>
</head>
<body>
<input type="text" name="t1" id="t1">
<input type="button" value="Submit" onclick="fabonacci_series()">
<div id=d1></div>
<script type="text/javascript">
function fabonacci_series(){
x=document.getElementById("t1").value
x=parseInt(x)
if(Number.isInteger(x)){
str='';
i=0
a=0
b=1
while(i<x){
	element=a+b
	a=b
	b=element
    str=str+ element+","
	i=i+1
}
document.getElementById('d1').innerHTML="Series is :  " + str
}else{
document.getElementById('d1').innerHTML="Enter an Integer  "	
}	
}
</script>
</body>
</html>

isInteger()	Checking if input number is integer or not
parseInt()	function to convert string to number

Next lower value of any decimal number JavaScript Basic JavaScript variable
JavaScript Math Reference

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Fabonacci series with number of elements by input number

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