files/en-us/web/javascript/reference/statements/if...else/index.md

---
title: if...else
slug: Web/JavaScript/Reference/Statements/if...else
page-type: javascript-statement
browser-compat: javascript.statements.if_else
sidebar: jssidebar
---

The **`if...else`** statement executes a statement if a specified condition is {{Glossary("truthy")}}. If the condition is {{Glossary("falsy")}}, another statement in the optional `else` clause will be executed.

{{InteractiveExample("JavaScript Demo: if...else statement")}}

```js interactive-example
function testNum(a) {
  let result;
  if (a > 0) {
    result = "positive";
  } else {
    result = "NOT positive";
  }
  return result;
}

console.log(testNum(-5));
// Expected output: "NOT positive"
```

## Syntax

```js-nolint
if (condition)
  statement1

// With an else clause
if (condition)
  statement1
else
  statement2
```

- `condition`
  - : An expression that is considered to be either {{Glossary("truthy")}} or {{Glossary("falsy")}}.
- `statement1`
  - : Statement that is executed if _condition_ is {{Glossary("truthy")}}. Can be any statement, including further nested `if` statements. To execute multiple statements, use a [block](/en-US/docs/Web/JavaScript/Reference/Statements/block) statement (`{ /* ... */ }`) to group those statements. To execute no statements, use an [empty](/en-US/docs/Web/JavaScript/Reference/Statements/Empty) statement.
- `statement2`
  - : Statement that is executed if `condition` is {{Glossary("falsy")}} and the `else` clause exists. Can be any statement, including block statements and further nested `if` statements.

## Description

Multiple `if...else` statements can be nested to create an `else if` clause. Note that there is no `elseif` (in one word) keyword in JavaScript.

```js-nolint
if (condition1)
  statement1
else if (condition2)
  statement2
else if (condition3)
  statement3
// …
else
  statementN
```

To see how this works, this is how it would look if the nesting were properly indented:

```js-nolint
if (condition1)
  statement1
else
  if (condition2)
    statement2
  else
    if (condition3)
      statement3
// …
```

To execute multiple statements within a clause, use a block statement (`{ /* ... */ }`) to group those statements.

```js-nolint
if (condition) {
  statements1
} else {
  statements2
}
```

Not using blocks may lead to confusing behavior, especially if the code is hand-formatted. For example:

```js-nolint example-bad
function checkValue(a, b) {
  if (a === 1)
    if (b === 2)
      console.log("a is 1 and b is 2");
  else
    console.log("a is not 1");
}
```

This code looks innocent — however, executing `checkValue(1, 3)` will log "a is not 1". This is because in the case of [dangling else](https://en.wikipedia.org/wiki/Dangling_else), the `else` clause will be connected to the closest `if` clause. Therefore, the code above, with proper indentation, would look like:

```js-nolint
function checkValue(a, b) {
  if (a === 1)
    if (b === 2)
      console.log("a is 1 and b is 2");
    else
      console.log("a is not 1");
}
```

In general, it is a good practice to always use block statements, especially in code involving nested `if` statements.

```js example-good
function checkValue(a, b) {
  if (a === 1) {
    if (b === 2) {
      console.log("a is 1 and b is 2");
    }
  } else {
    console.log("a is not 1");
  }
}
```

Do not confuse the primitive Boolean values `true` and `false` with truthiness or falsiness of the {{jsxref("Boolean")}} object. Any value that is not `false`, `undefined`, `null`, `0`, `-0`, `NaN`, or the empty string (`""`), and any object, including a Boolean object whose value is `false`, is considered {{Glossary("truthy")}} when used as the condition. For example:

```js
const b = new Boolean(false);
if (b) {
  console.log("b is truthy"); // "b is truthy"
}
```

## Examples

### Using if...else

```js
if (cipherChar === fromChar) {
  result += toChar;
  x++;
} else {
  result += clearChar;
}
```

### Using else if

Note that there is no `elseif` syntax in JavaScript. However, you can write it with a space between `else` and `if`:

```js
if (x > 50) {
  /* do something */
} else if (x > 5) {
  /* do something */
} else {
  /* do something */
}
```

### Using an assignment as a condition

You should almost never have an `if...else` with an assignment like `x = y` as a condition:

```js example-bad
if ((x = y)) {
  // …
}
```

Because unlike {{jsxref("Statements/while", "while")}} loops, the condition is only evaluated once, so the assignment is only performed once. The code above is equivalent to:

```js example-good
x = y;
if (x) {
  // …
}
```

Which is much clearer. However, in the rare case you find yourself wanting to do something like that, the [`while`](/en-US/docs/Web/JavaScript/Reference/Statements/while) documentation has a [Using an assignment as a condition](/en-US/docs/Web/JavaScript/Reference/Statements/while#using_an_assignment_as_a_condition) section with our recommendations.

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- {{jsxref("Statements/block", "block")}}
- {{jsxref("Statements/switch", "switch")}}
- [Conditional (ternary) operator](/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_operator)