Array.prototype.slice()

Method slice() mengembalikan sebuah salinan dangkal dari sebagian array menjadi sebuah objek array baru yang dimulai dari start sampai end (end tidak termasuk) dimana start dan end merupakan index dari  item yang ada di  array tersebut. Tidak merubah array asli.

Sintaks

arr.slice([start[, end]])

Parameter

start Optional
Indeks berbasis nol untuk memulai ekstraksi.

Indeks negatif dapat digunakan, menunjukkan offset dari akhir urutan.. slice(-2) mengekstrak dua elemen terakhir dari urutan.
Jika start tidak terdefinisi, slice memulai dari indeks ke 0.
Jika start lebih besar dari indeks urutan, array kosong akan dikembalikan.
end Optional
Indeks berbasis nol untuk mengakhiri ekstraksi. slice mengekstrak hingga tapi tidak termasuk end. Sebagai contoh, slice(1,4) mengekstrak elemen kedua menuju elemen ke-empat (indeks elemen 1, 2, dan 3).

Indeks negatif bisa digunakan,
menunjukkan offset dari akhir urutan. slice(2,-1) mengekstrak elemen ketiga menuju elemen kedua-ke-terakhir dalam urutan.

Jika end dihillangkan, slice mengekstrak melalui akhir dari urutan (arr.length).
Jika end lebih besar dari panjang urutan, slice mengkstrak melalui akhir urutan (arr.length).

Return value

Array baru berisi elemen yang diekstrak.

Deskripsi

slice does not alter the original array. It returns a shallow copy of elements from the original array. Elements of the original array are copied into the returned array as follows:

  • For object references (and not the actual object), slice copies object references into the new array. Both the original and new array refer to the same object. If a referenced object changes, the changes are visible to both the new and original arrays.
  • For strings, numbers and booleans (not String, Number and Boolean objects), slice copies the values into the new array. Changes to the string, number, or boolean in one array do not affect the other array.

If a new element is added to either array, the other array is not affected.

Contoh

Return a portion of an existing array

let fruits = ['Banana', 'Orange', 'Lemon', 'Apple', 'Mango']
let citrus = fruits.slice(1, 3)

// fruits contains ['Banana', 'Orange', 'Lemon', 'Apple', 'Mango']
// citrus contains ['Orange','Lemon']

Using slice

In the following example, slice creates a new array, newCar, from myCar. Both include a reference to the object myHonda. When the color of myHonda is changed to purple, both arrays reflect the change.

// Using slice, create newCar from myCar.
let myHonda = { color: 'red', wheels: 4, engine: { cylinders: 4, size: 2.2 } }
let myCar = [myHonda, 2, 'cherry condition', 'purchased 1997']
let newCar = myCar.slice(0, 2)

// Display the values of myCar, newCar, and the color of myHonda
//  referenced from both arrays.
console.log('myCar = ' + JSON.stringify(myCar))
console.log('newCar = ' + JSON.stringify(newCar))
console.log('myCar[0].color = ' + myCar[0].color)
console.log('newCar[0].color = ' + newCar[0].color)

// Change the color of myHonda.
myHonda.color = 'purple'
console.log('The new color of my Honda is ' + myHonda.color)

// Display the color of myHonda referenced from both arrays.
console.log('myCar[0].color = ' + myCar[0].color)
console.log('newCar[0].color = ' + newCar[0].color)

This script writes:

myCar = [{color: 'red', wheels: 4, engine: {cylinders: 4, size: 2.2}}, 2,
         'cherry condition', 'purchased 1997']
newCar = [{color: 'red', wheels: 4, engine: {cylinders: 4, size: 2.2}}, 2]
myCar[0].color = red
newCar[0].color = red
The new color of my Honda is purple
myCar[0].color = purple
newCar[0].color = purple

Array-like objects

slice method can also be called to convert Array-like objects/collections to a new Array. You just bind the method to the object. The arguments inside a function is an example of an 'array-like object'.

function list() {
  return Array.prototype.slice.call(arguments)
}

let list1 = list(1, 2, 3) // [1, 2, 3]

Binding can be done with the call() method of Function.prototype and it can also be reduced using [].slice.call(arguments) instead of Array.prototype.slice.call.

Anyway, it can be simplified using bind.

let unboundSlice = Array.prototype.slice
let slice = Function.prototype.call.bind(unboundSlice)

function list() {
  return slice(arguments)
}

let list1 = list(1, 2, 3) // [1, 2, 3]

Spesifikasi

Kompatibilitas Peramban

BCD tables only load in the browser

Lihat juga