let x = 9.656;
x.toPrecision();
x.toPrecision(2);
x.toPrecision(4);
x.toPrecision(6);
<!DOCTYPE html>
<html>
<body>
<h1>JavaScript Numbers</h1>
<h2>The toPrecision() Method</h2>
<p>toPrecision() formats a number to a specified length:</p>
<p id="demo"></p>
<script>
let num = 0.001658853;
document.getElementById("demo").innerHTML =
num.toPrecision(2) + "<br>" +
num.toPrecision(3) + "<br>" +
num.toPrecision(10);
</script>
</body>
</html>