if...else

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 statement ({ /* ... */ }) to group those statements. To execute no statements, use an 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.

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:

if (condition1)
  statement1
else
  if (condition2)
    statement2
  else
    if (condition3)
      statement3
// …

The conditions are evaluated in order until one evaluates to true. At that point, the associated statement is executed and the rest of the else if clauses are skipped.

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

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#

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:

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 documentation has a 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