Instrucción throw de JavaScript

Definición y uso

La instrucción throw lanza (produce) errores.

Cuando ocurre un error, JavaScript generalmente se detendrá y generará un mensaje de error.

Su terminología técnica es: JavaScript lanzará (throw) errores.

La instrucción throw permite crear errores personalizados.

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

Exceptions can be JavaScript strings, numbers, booleans, 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, or object.

technical details

JavaScript version： ECMAScript 3

browser support

statement Chrome IE Firefox Safari Opera
throw Soporte Soporte Soporte Soporte Soporte

Páginas relacionadas

Tutoriales de JavaScript:Errores de JavaScript

Manual de referencia de JavaScript:Sentencia try/catch/finally de JavaScript