73 lines
1.7 KiB
Markdown
73 lines
1.7 KiB
Markdown
---
|
|
title: If-Else Statement
|
|
---
|
|
## Introduction
|
|
|
|
The `if` statement executes a statement if a specified condition is `true`. If the condition is `false`, another statement can be executed using the `else` statement.
|
|
|
|
**Note:** The `else` statement is optional.
|
|
|
|
```javascript
|
|
if (condition)
|
|
/* do something */
|
|
else
|
|
/* do something else */
|
|
```
|
|
|
|
|
|
Multiple `if...else` statements can be chained to create an `else if` clause. This specifies a new condition to test and can be repeated to test multiple conditions, checking until a true statement is presented to execute.
|
|
|
|
```javascript
|
|
if (condition1)
|
|
/* do something */
|
|
else if (condition2)
|
|
/* do something else */
|
|
else if (condition3)
|
|
/* do something else */
|
|
else
|
|
/* final statement */
|
|
```
|
|
|
|
**Note:** If you want to execute more than one statement in the `if`, `else` or `else if` part, curly braces are required around the statements:
|
|
|
|
```javascript
|
|
if (condition) {
|
|
/* do */
|
|
/* something */
|
|
/* with multiple statements */
|
|
} else {
|
|
/* do something */
|
|
/* else */
|
|
}
|
|
```
|
|
|
|
<a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/if...else' target='_blank' rel='nofollow'>MDN link</a> | <a href='https://msdn.microsoft.com/en-us/library/85yyde5c.aspx' target='_blank' rel='nofollow'>MSDN link</a>
|
|
|
|
## Examples
|
|
|
|
**Using** `if...else`:
|
|
```javascript
|
|
// If x=5 then z=7 and q=42 else z=19.
|
|
if (x === 5) {
|
|
z = 7;
|
|
q = 42;
|
|
}else{
|
|
z = 19;
|
|
}
|
|
```
|
|
|
|
**Using** `else if`:
|
|
|
|
```javascript
|
|
if (x < 10){
|
|
return "Small number";
|
|
}else if (x < 50){
|
|
return "Medium number";
|
|
}else if (x < 100){
|
|
return "Large number";
|
|
}else {
|
|
flag = 1;
|
|
return "Invalid number";
|
|
}
|
|
```
|