Detect Generator Functions with JavaScript

By  on  

In the current JavaScript climate of new syntaxes, features, and using loads of external libraries, it seems harder than ever to be sure what your functions are being given or even what the data represents. Of course, we've come up with Flow and TypeScript to help, but we can't count on those always being available. That's why I like doing my own detection with JavaScript, especially when it comes to function types.

To detect if a function is a generator or async generator function, you can use the following code:

// Sample generator function
function* sampleGenerator() {}
sampleGenerator.constructor.name
// "GeneratorFunction"

async function* sampleGenerator() {}
sampleGenerator.constructor.name
// "AsyncGeneratorFunction"

Coincidentally, you can also detect a regular async function with:

async function asyncThing() {}
asyncThing.constructor.name
// "AsyncFunction"

It's always important to know if the code you're using is sync, async, or a generator, but if you're using external libraries or want to write comprehensive tests, these types of detections may be necessary.

Recent Features

  • By
    CSS Gradients

    With CSS border-radius, I showed you how CSS can bridge the gap between design and development by adding rounded corners to elements.  CSS gradients are another step in that direction.  Now that CSS gradients are supported in Internet Explorer 8+, Firefox, Safari, and Chrome...

  • By
    Create a CSS Flipping Animation

    CSS animations are a lot of fun; the beauty of them is that through many simple properties, you can create anything from an elegant fade in to a WTF-Pixar-would-be-proud effect. One CSS effect somewhere in between is the CSS flip effect, whereby there's...

Incredible Demos

  • By
    CSS Counters

    Counters.  They were a staple of the Geocities / early web scene that many of us "older" developers grew up with;  a feature then, the butt of web jokes now.  CSS has implemented its own type of counter, one more sane and straight-forward than the ole...

  • By
    Custom Scrollbars in WebKit

    Before each of the browser vendors we like was providing unique CSS controls, Internet Explorer was setting the tone.  One such example is IE's early implementation of CSS filters. Internet Explorer was also the first browser that allowed developers to, for better or worse, customize...

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!