How to check whether the values are safe integers in javascript?

Html page:

<button onclick="myFunction()">Try it</button>

<p id="P8"></p>

Javascript page:

<script>

    function myFunction() {

        var res = "";

        res = res + Number.isSafeInteger(123) + ": 123<br>";

        res = res + Number.isSafeInteger(-123) + ": -123<br>";

        res = res + Number.isSafeInteger(5 - 2) + ": 5-2<br>";

        document.getElementById("demo").innerHTML = res;

    }

</script>

Output:

true: 123

true: -123

true: 5-2