Expression throw en JavaScript

Définition et utilisation

La directive throw lève (génère) des erreurs.

Lorsqu'une erreur se produit, JavaScript s'arrête généralement et génère un message d'erreur.

Son terme technique est : JavaScript lève (throw) des erreurs.

La directive throw permet de créer des erreurs personnalisées.

Its technical term is: throw an exception (exception).

Exceptions can be JavaScript strings, numbers, boolean values, or objects:

throw "Too big";    // Throw text
throw 500;          // Throw a number

When used with try and catch, throw can control the program flow and generate custom error messages.

For more information on JavaScript errors, please study our JavaScript error tutorial.

Example

This example checks the input. If the value is incorrect, it throws an exception (err).

The catch statement catches the exception (err) and displays a custom error message:

<!DOCTYPE html>
<html>
<body>
<p>Please input a number between 5 and 10:</p>
<input id="demo" type="text">
<button type="button" onclick="myFunction()">Test Input</button>
<p id="message"></p>
<script>
function myFunction() {
  var message, x;
  message = document.getElementById("message");
  message.innerHTML = "";
  x = document.getElementById("demo").value;
  try { 
    if(x == "") throw "is Empty";
    if(isNaN(x)) throw "not a number";
    if(x > 10) throw "too high";
    if(x < 5) throw "too low";
  }
  catch(err) {
    message.innerHTML = "Input " + err;
  }
}
</script>
</body>
</html>

try it yourself

syntax

throw expression;

parameter value

parameter description
expression necessary. The exception to be thrown. It can be a string, number, boolean value, or object.

technical details

JavaScript version: ECMAScript 3

browser support

expression Chrome IE Firefox Safari Opera
throw Support Support Support Support Support

Pages associées

Tutoriel JavaScript :Erreurs JavaScript

Manuel de référence JavaScript :Instructions try/catch/finally JavaScript