1var number = 12.3456789;
2var rounded = Math.round( number * 10 ) / 10;
3// rounded is 12.3

1let num = 12.5452411;
2num = num.toFixed(3); // 12.545

1Math.round(3.14159)  // 3
2Math.round(3.5)      // 4
3Math.floor(3.8)      // 3
4Math.ceil(3.2)       // 4
5

1myNumber.toFixed(7);