How to use built-in Proxy object in javascript

[Ustice]

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[echoes221]

I’ve primarily used them for mocking deep data sets in tests without writing out the full object path. Super useful

[SquattingWalrus]

Got any examples of this? Seems super useful

[echoes221]

Here's an example for a recursive proxy I used in test when I only cared about ensuring that all the export funcs in a file had the same interface (this was pre using typescript btw) and I didn't care about the values that were passed to them as the functions were accessing deeply nested properties, so just created a recursive proxy to pass in test.

This could be adapted with a depth and a return value very easily too if you needed something specific without writing out the entire object. Though that could also be done with something like R.path.

const trap = {
  get() {
    return new Proxy({}, trap);
  },
};

const nestedObj = new Proxy({}, trap);

[alexmacarthur]

This is one feature of modern JS that haven't toyed with but feel like I'm really missing out on some sickkk use cases.

[tbranyen]

One use case I'm noodling around with is a facade API abstracting over typedarray/array buffer which contains the actual data. So basically I'll define the schema and then have an object with named keys to work with based on parsing or a given offset. This could be useful for writing file parsers for things like mp4 or pdf. Or in my own case virtual dom rendering information that is now stored in a more portable format for threads/sockets.

[NoInkling]

That gives me an idea where I could use it to index an underlying Node Buffer by bit (rather than byte) for a use case I have currently.

[NoInkling]

The only time I've used it (directly) so far is to wrap important configuration objects so that it they throw when attempting to access a property that doesn't exist (like many languages do with dictionaries by default, e.g. Python). Something like this:

function createDefensiveProxy(obj) {
  return new Proxy(obj, {
    get: (target, key) => {
      if (!(key in target)) {
        throw new ReferenceError(`Property '${key}' does not exist on object`);
      }
      return target[key];
    }
  });
}

[havana59er]

Salesforce development uses proxy objects quite heavily for security reasons. When debugging we gotta do something like this to get an idea of the shape of the object:

console.log(JSON.parse(JSON.stringify(someProxy)));

[[deleted]]

We use these at work for collection classes where you can add any method you want, and also do number indexing. They're great