A safe integer is an integer represented as an IEEE-754 double-precision number. That would mean integers from (253 - 1) to -(253 - 1). To check whether a value is a safe integer or not in JavaScript, use the isSafeInteger() method.
Example
You can try to run the following code to check whether a value is a safe integer or not. It returns true for a safe integer and integer −
<!DOCTYPE html>
<html>
<body>
<script>
document.write("Checking for Safe Integer...");
document.write("<br>"+Number.isSafeInteger(765));
document.write("<br>"+Number.isSafeInteger(-765));
document.write("<br>"+Number.isSafeInteger('765'));
document.write("<br>"+Number.isSafeInteger(false));
document.write(Number.isSafeInteger(Math.pow(2, 53) - 1));
</script>
</body>
</html>