Lodash's `map()` Function
Apr 8, 2020
Given an array arr and a function fn, Lodash's map() function returns an array containing the return values of fn() on every element in the array.
const arr = [1, 2, 3, 4];
_.map(arr, v => v * 2); // [2, 4, 6, 8]On Arrays of Objects
Given an array of objects, you can pass a string as fn instead of a function
to get array containing each object's value for the property fn.
const arr = [
{ firstName: 'Will', lastName: 'Riker', rank: 'Commander' },
{ firstName: 'Beverly', lastName: 'Crusher', rank: 'Commander' },
{ firstName: 'Wesley', lastName: 'Crusher', rank: 'Ensign' }
];
_.map(arr, 'firstName'); // ['Will', 'Beverly', 'Wesley']
// Equivalent:
_.map(arr, v => v.firstName); // ['Will', 'Beverly', 'Wesley']On Objects
You can also call _.map() on an object. _.map(obj, fn) behaves like
_.map(Object.values(obj), fn).
const obj = {
one: 1,
two: 2,
three: 3,
four: 4
};
_.map(obj, v => v * 2); // [2, 4, 6, 8]
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