Pick matching object keys

JavaScript, Object · Oct 22, 2020

Creates an object composed of the properties the given function returns truthy for.

Use Object.keys() and Array.prototype.filter()to remove the keys for which fn returns a falsy value.
Use Array.prototype.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
The callback function is invoked with two arguments: (value, key).

const pickBy = (obj, fn) =>
  Object.keys(obj)
    .filter(k => fn(obj[k], k))
    .reduce((acc, key) => ((acc[key] = obj[key]), acc), {});

pickBy({ a: 1, b: '2', c: 3 }, x => typeof x === 'number');
// { 'a': 1, 'c': 3 }

Finds all the keys in the provided object that match the given value.

JavaScript, Object · Nov 15, 2020

Omits the key-value pairs corresponding to the keys of the object for which the given function returns falsy.

JavaScript, Object · Oct 21, 2020

Finds the first key that satisfies the provided testing function. Otherwise undefined is returned.

JavaScript, Object · Oct 22, 2020

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