Today I Learned

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Matching A Computed Property In Function Args

The computed property name feature of ES6 allows you to reference a variable in object assignments and destructurings. This syntax is flexible enough that it can be used in the arguments portion of a function declaration. In fact, it can even be matched against another argument — allowing the creation of some handy, yet terse functions.

const get = (key, { [key]: foundValue }) => foundValue;

Notice that the first argument, key, will match against the computed property name in the second argument. The foundValue will correspond to whatever key maps to in the given object.

This get function can then be used like so.

const stuff = { a: 1, b: 2, c: 3 };

console.log("Get a:", get("a", stuff)); // Get a: 1
console.log("Get d:", get("d", stuff)); // Get d: undefined

h/t @sharifsbeat

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