The toPrecision() method returns a string, with a number written with a specified length.
let a = 5.456;
console.log(a.toPrecision()); // 5.456
console.log(a.toPrecision(2)); // 5.5
console.log(a.toPrecision(4)); // 5.456
console.log(a.toPrecision(6)); // 5.45600
