Javascript - Math Rounding Methods

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Introduction

Math.ceil(), Math.floor(), and Math.round() - handle rounding in different ways:

Method Description
Math.ceil() rounds numbers up to the nearest integer value.
Math.floor() rounds numbers down to the nearest integer value.
Math.round() a standard round function, which rounds up if the number is at least halfway to the next integer value (0.5 or higher) and rounds down if not.

The following example illustrates how these methods work: 

console.log(Math.ceil(5.9));     
console.log(Math.ceil(5.5));     
console.log(Math.ceil(5.1));     

console.log(Math.round(5.9));    
console.log(Math.round(5.5));    
console.log(Math.round(5.1));    

console.log(Math.floor(5.9));    
console.log(Math.floor(5.5));    
console.log(Math.floor(5.1));

For all values between 5 and 6 (exclusive), Math.ceil() always returns 6, because it will always round up.

The Math.round() method returns 6 only if the number is 5.5 or greater; otherwise it returns 25.

Math.floor() returns 5 for all numbers between 5 and 6 (exclusive).