JavaScript: throw statement

Last update on May 28 2022 10:26:54 (UTC/GMT +8 hours)

Description

The throw statement creates a user define exception.
You can create your own exception for unexpected events and control the script properly to throw the exception in a try block and handle it in the catch block.

Syntax

throw exception;

Parameters

exception: String, integer, Boolean or an object.

Example of try..catch..throw statement

The following example checks the length of a variable called empcode. If the value of empcode is greater than 8 or less than 3 then the code throws an error and caught by the catch argument and an appropriate message will be displayed.

HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset=utf-8>
<title>JavaScript try..catch..throw Example</title>
</head>
<body>
<h1 style="color: red">JavaScript : try..catch..throw Example</h1>
<hr />
<script src="try-catch-throw-example.js"></script>
</body>
</html>

JS Code

var empcode = prompt("Input the Employee code : (Between 3 to 8 characters):","");
try
{
if(empcode.length>8)
 {
 throw "error1";
 }
else if(empcode.length<3)
 {
  throw "error2";
 }
 }
catch(err)
 {
 if(err=="error1")
 {
 console.log("The Employee code length exceed 8 characters.");
 }
 if(err=="error2")
 {
 console.log("The Employee code length is less than 3 characters");
 }
 }

View the example in the browser

Practice the example online

See the Pen throw-1 by w3resource (@w3resource) on CodePen.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04