The JavaScript if/else conditional: A Guide

Learn the basics of using the JavaScript if conditional in your code.

An if statement is a powerful tool in JavaScript that allows you to control the flow of your program based on the evaluation of an expression. By using conditionals, you can make your program take different paths depending on certain conditions.

Let’s start with a simple example that always executes:

if (true) {
  // code to be executed
}

In this case, the code inside the if block will always run because the expression true evaluates to true.

On the contrary, if the expression evaluates to false, the code inside the if block will never execute:

if (false) {
  // code to be executed (never)
}

If you only have a single statement to execute after the conditional, you can omit the curly braces and just write the statement:

if (true) doSomething();

The if statement checks the expression you pass to it for a true or false value. When you pass a number, it always evaluates to true unless it’s 0. Similarly, when you pass a string, it evaluates to true unless it’s an empty string. These are the general rules for casting types to a boolean.

The Else Statement

In addition to the if statement, you can also use the else statement to provide an alternative code block to execute when the if condition is false:

if (true) {
  // code to be executed
} else {
  // alternative code to be executed
}

Here, if the expression inside the if statement evaluates to true, the code block inside the if block will be executed. Otherwise, the code inside the else block will be executed.

To add more complexity, you can nest another if/else statement inside the else block:

if (a === true) {
  // code to be executed
} else if (b === true) {
  // code to be executed
} else {
  // fallback code to be executed
}

In this case, if the condition a === true is true, the first code block will execute. If it’s false and the condition b === true is true, the second code block will execute. If both conditions are false, the fallback code block will be executed.

By mastering the if and else statements, you can create dynamic and flexible code that responds to different conditions.

The Else Statement#

The Else Statement