Getting properties from objects that match a condition
Need to get an attribute of all objects in an array that match a condition? Chain Array.prototype.filter() and Array.prototype.map() to first filter the list to all the elements you want and then get the values you’re looking for.
// this array contains objects that have a `name` and `type`
const food = [
{
name: 'Apple',
type: 'fruit'
}, {
name: 'Banana',
type: 'fruit'
}, {
name: 'Cucumber',
type: 'vegetable'
}
]
// we can first get all objects that have their `type` set to 'fruit'
const fruit = food.filter(element => element.type === 'fruit')
// ⇒ [
// {
// name: 'Apple',
// type: 'fruit'
// }, {
// name: 'Banana',
// type: 'fruit'
// }
// ]
// we can then use `.map()` to extract their names
const fruitNames = fruit.map(element => element.name)
// ⇒ ['Apple', 'Banana']
// we can do both steps at once by chaining `.filter()` and `.map()`
const fruitNames = food
.filter(element => element.type === 'fruit') // get all fruit
.map(element => element.name) // extract their names
// ⇒ ['Apple', 'Banana']