numbers.js

var pi = 3.141;
pi.toFixed(0); // returns 3
pi.toFixed(2); // returns 3.14 - for working with money
pi.toPrecision(2); // returns 3.1
pi.valueOf(); // returns number
Number(true); // converts to number
Number(new Date()); // number of milliseconds since 1970
parseInt("3 months"); // returns the first number: 3
parseFloat("3.5 days"); // returns 3.5
Number.MAX_VALUE; // largest possible JS number
Number.MIN_VALUE; // smallest possible JS number
Number.NEGATIVE_INFINITY; // -Infinity
Number.POSITIVE_INFINITY; // Infinity