Logical Operators Part 1

Part of the Fundamentals section of Coddy's JavaScript journey — lesson 18 of 77.

Logical operators are used to check combinations of comparisons that return true or false.

For example, the following statement contains two comparisons:

Is 5 greater than 3 and less than 6?

Operator	Meaning	Example
`&&`	And - `true` if all operands are `true`	`a && b`
`\|\|`	Or - `true` if any operand is `true`	`a \|\| b`
`!`	Not - `true` if the operand is `false`	`!a`

Let's see some examples:

5 is greater than 3, and 1 equals 1:

let b1 = (5 > 3) && (1 == 1); // holds true

Explanation: All of the operands are true, so b1 will hold true (&& operation is true if both operands are true) .

5 is not equal to 4, or five equals to 2:

let b2 = !(5 == 4) || (5 == 2); // holds true

Explanation: The first operand (5 != 4) is true so b2 is also true (|| operation is true if either one of the operands is true)

1 is not equal to 1 or false:

let b3 = !(1 == 1) || false; // holds false

Explanation: All of the operands are false, so b3 will hold false (|| operation).

not (3 greater than 4):

let b4 = !(3 > 4); // holds true

Explanation: The operand is false, so b4 will hold true (! operation).

not (5 greater than 10 or 5 greater than 1):

let b5 = !(5 > 10 || 5 > 1); // holds false

Explanation: 5 > 10 || 5 > 1 is true (one of the operands is true), so in total b5 is false (! operation).

Challenge

Beginner

You are given a code. Replace the question marks of the variables b1 and b2 so that b3 holds true.

There are many right solutions.

Cheat sheet

Logical operators are used to check combinations of comparisons that return true or false.

Operator	Meaning	Example
`&&`	And - `true` if all operands are `true`	`a && b`
`\|\|`	Or - `true` if any operand is `true`	`a \|\| b`
`!`	Not - `true` if the operand is `false`	`!a`

Examples:

let b1 = (5 > 3) && (1 == 1); // true - both operands are true
let b2 = !(5 == 4) || (5 == 2); // true - first operand is true
let b3 = !(1 == 1) || false; // false - all operands are false
let b4 = !(3 > 4); // true - operand is false, so ! makes it true
let b5 = !(5 > 10 || 5 > 1); // false - expression inside is true, ! makes it false

Try it yourself

// Type your code below
let b1 = ?
let b2 = ?
let b3 = b1 || b2

// Don't change the line below
console.log(`b3 = ${b3}`)

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

The Language Hello World!Comments Code Structure

4Operators Part 2

Logical Operators Part 1Logical Operators Part 2 Recap - Simple Logic Logical Operators Part 3 Type Coercion

7Bill Split Calculator

Welcome Message Calculating The Tip And Total

Splitting The Bill

Formatted Output

10FizzBuzz with a Twist

Game Overview The FizzBuzz Function

Looping The Numbers

Adding The Twist

13Grocery List Tracker

Project Overview Add Item

Remove Item

View List