Floor Division in JavaScript

TL ; DR:

• The Math.floor() function returns the largest integer less than or equal to a given number:

  console.log(Math.floor(3.9)); // Output: 3
  console.log(Math.floor(5.2)); // Output: 5
  console.log(Math.floor(7)); // Output: 7
  

• We can use this function if we want to compute the integral part of some division (quotient):

  let a = 3;
  let b = 7;
  
  console.log(Math.floor(20 / a)); // Output: 6
  console.log(Math.floor(b / a)); // Output: 2
  

Full lesson:

Remember how we first learn about the division of two integer numbers in primary school?

The quotient is the number of times a division is completed fully, while the remainder is the amount left that doesn't entirely go into the divisor.

Here are some examples:

10 / 2 = quotient 5, remainder 0
15 / 4 = quotient 3, remainder 3
20 / 3 = quotient 6, remainder 2

Floor division

In JavaScript, / keeps the decimals: 15 / 4 is 3.75. To get only the integral part (the quotient), wrap the division in Math.floor():

console.log(Math.floor(10 / 2)); // Output: 5
console.log(Math.floor(15 / 4)); // Output: 3
console.log(Math.floor(20 / 3)); // Output: 6

It can also be used with variables:

let a = 3;
let b = 7;

console.log(Math.floor(20 / a)); // Output: 6
console.log(Math.floor(b / a)); // Output: 2

Modulo

The modulo operator (%) calculates the remainder of dividing two values:

console.log(10 % 2); // Output: 0
console.log(15 % 4); // Output: 3
console.log(20 % 3); // Output: 2

// Can be used with variables:
let x = 2;
let y = 4;

console.log(y % x); // Output: 0
console.log(11 % y); // Output: 3

Quotient and remainder

In programming, we combine both these concepts to get the quotient and remainder of a division:

// Let's divide 26 by 3:
let quotient = Math.floor(26 / 3);
let remainder = 26 % 3;

console.log(quotient); // Output: 8
console.log(remainder); // Output: 2

Assignment
Follow the Coding Tutorial and let's practice with quotient and remainder!

Hint
Look at the examples above if you get stuck.