72 lines
1.7 KiB
Markdown
72 lines
1.7 KiB
Markdown
---
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title: If-Else Statement
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---
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## Introduction
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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.
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**Note:** The `else` statement is optional.
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```javascript
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if (condition)
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/* do something */
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else
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/* do something else */
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```
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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.
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```javascript
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if (condition1)
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/* do something */
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else if (condition2)
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/* do something else */
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else if (condition3)
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/* do something else */
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else
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/* final statement */
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```
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**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:
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```javascript
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if (condition) {
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/* do */
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/* something */
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/* with multiple statements */
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} else {
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/* do something */
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/* else */
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}
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```
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<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>
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## Examples
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**Using** `if...else`:
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```javascript
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// If x=5 z=7 and q=42. If x is not 5 then z=19.
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if (x == 5) {
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z = 7;
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q = 42
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else
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z = 19;
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```
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**Using** `else if`:
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```javascript
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if (x < 10)
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return "Small number";
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else if (x < 50)
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return "Medium number";
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else if (x < 100)
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return "Large number";
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else {
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flag = 1;
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return "Invalid number";
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}
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```
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