Javascript has provided isFinite() method to check whether the given entity is a legal number or not. If the given entity is a number, regardless of string for instance "123", this method will result in boolean true, else returns false. Let's discuss it in a nutshell.
syntax
isFinite(value);
This method takes a value as a parameter and returns boolean true if the value passed is a number else returns a boolean false.
Example-1
In the following example, numbers were sent into the method isFinite() as parameters and the result is displayed in the output.
<html>
<body>
<p id = "number"></p>
<script>
var a = isFinite(567) + "</br>";
var b = isFinite(-9.23) + "</br>";
var c = isFinite(0) + "</br>";
var d = isFinite(6-7) + "</br>";
var bol = a + b + c + d;
document.getElementById("number").innerHTML = bol;
</script>
</body>
</html>Output
true true true true
Example-2
In the following example, strings and date were passed as parameters. This method accepts the number strings as a number and returns true as output.
<html>
<body>
<p id = "number"></p>
<script>
var x = isFinite("123") + "<br>";
var y = isFinite("string") + "<br>";
var z = isFinite("2019/08/06");
var res = x + y + z ;
document.getElementById("number").innerHTML = res;
</script>
</body>
</html>Output
true false false