Format numbers in javascript

var num = 1;
var result = num.toFixed(2); // result = 1.00

num = 123.4567;
result = num.toFixed(3); // result = 123.456

num = 123.4567;
result = num.toPrecision(4); // result = 123.4

num = 123.4567;
result = num.toPrecision(3); // result = 123

num = 555.55;
result = num.toPrecision(2); // result will equal 5.6e+2

see also this article.