errores de captura de javascript, nulo

When using the following syntax, would the output in console be out ?

I am making sure that I'm catching errors in callbacks and responding properly.

var err = null;

if (err) {
    console.log ("in");
} else {
    console.log ("out");
}

preguntado el 28 de enero de 14 a las 18:01

yes, null is "falsey" -

@jalynn2 perfect :) thanks! -

null, undefined, false, 0 etc.. will print out -

Why haven't you simply tried it out? -

This question appears to be off-topic because it is something that could have easily been answered in 2 seconds by the poster trying it out himself. -

3 Respuestas

If your value is one of the following:

  • 0
  • nulo
  • ""
  • false
  • indefinido
  • Yaya

the object is set to false. For any other value it is set to true.

Respondido el 28 de enero de 14 a las 18:01

Using either your browser's JavaScript console or a site like http://repl.it/ can be really helpful to test logical expressions. One thing you can always do if you're not sure about the truthiness of an expression (doesn't matter as much for a simple case like this, but can be especially helpful when debugging with watch expressions or conditional breakpoints) is cast it to boolean (true/false) by using the ! operator twice. For example:

  • !!null === false // true
  • !!0 === false // true
  • !![] === true // true

Respondido el 28 de enero de 14 a las 18:01

The answer is Yes. But you can test it yourself by running in the browser.

Respondido el 28 de enero de 14 a las 18:01

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