Finds the last key that satisfies the provided testing function.
Otherwise undefined
is returned.
Object.keys()
to get all the properties of the object.Array.prototype.reverse()
to reverse the order and Array.prototype.find()
to test the provided function for each key-value pair.const findLastKey = (obj, fn) =>
Object.keys(obj)
.reverse()
.find(key => fn(obj[key], key, obj));
findLastKey(
{
barney: { age: 36, active: true },
fred: { age: 40, active: false },
pebbles: { age: 1, active: true }
},
x => x['active']
); // 'pebbles'
JavaScript, Object
Finds the first key that satisfies the provided testing function.
Otherwise undefined
is returned.
JavaScript, Object
Finds all the keys in the provided object that match the given value.
JavaScript, Object
Maps the keys of an object using the provided function, generating a new object.