    function decimals(n, d) {  
     if ((typeof n !== 'number') || (typeof d !== 'number'))  
       return false;  
            n = parseFloat(n) || 0;  
        return n.toFixed(d);  
        }  
    console.log(decimals(2.100212, 2));  
    console.log(decimals(2.100212, 3));  
    console.log(decimals(2100, 2));  