Array λ΄μ₯ν¨μ π
(1) map
- mapμ λ°°μ΄μ μν νλͺ©μ λ³νν λ μ¬μ©!
μ΄λ€ λ°°μ΄μ μν νλͺ©μ μνλ λλ‘ λ³ννκ³ , μλ‘μ΄ λ°°μ΄λ‘ λ§λ€μ΄μ€
μλ³Έ λ°°μ΄μ κ°μ΄ λ³νμ§ μμ.
const array_num = [0,1,2,3,4,5];
const new_array = array_num.map((array_item) => {
return array_item + 1;
});
console.log(new_array) = [1,2,3,4,5,6]; //μλ‘μ΄λ°°μ΄
console.log(array_num) = [0,1,2,3,4,5]; //μλ³Έλ°°μ΄
(2) filter
- μ΄λ€ 쑰건μ λ§μ‘±νλ νλͺ©λ§ 골λΌμ μλ°°μ΄λ‘!
μλ³Έ λ°°μ΄μ λ³νμ§ μκ³ μνλ λ°°μ΄μ νλλ λ§λ€μμλ€!
const array_num = [0,1,2,3,4,5];
const new_array = array_num.filter((array_item) => {
return array_item > 3 });
[4,5]
(3) concat
- λ°°μ΄κ³Ό λ°°μ΄μ ν©μΉκ±°λ, μΆκ°ν λ ! μ΄κ²λ μλ³Έλ°°μ΄ λ³νX
but !! μ€λ³΅ κ° λΉΌμ£Όμ§ μκ³ κ·Έλλ‘ λ€ λ€μ΄κ°
λ€λ₯Έ λ΄μ₯ν¨μμ ν¨κ» μ¬μ©ν΄μ μ κ±°ν΄μΌνλ€.
const array_num1 = [0,1,2,3]
const array_num2 = [3,4,5]
const merge = array_num1.concat(array_num2);
[0,1,2,3,3,4,5]
**but**
const new_merge = [...new Set(array_num1.concat(array_num2))]
//μ€λ³΅μλ£ μμ μ£Όλν¨μ~ ...μΌλ‘ λ°κΉ₯μΌλ‘ κΊΌλ΄μ λ€μ λ°°μ΄[]
[1,2,3,4,5]
(4) from
- λ°°μ΄λ‘ λ§λ€κ³ μΆμ λ, μ μ¬λ°°μ΄ 볡μ¬ν΄μ μκ±° λ§λ€ λ,
μ¬κΈ°μ μ μ¬λ°°μ΄μ΄λ [μ΄λ€κ°λ€...] μ²λΌ μκ²Όκ³ ,
λ°°μ΄μ λ΄μ₯ ν¨μλ₯Ό μ¬μ©λͺ»νλ κ².
- μλ‘μ΄ λ°°μ΄ λ§λλ κ²μ΄λΌ μκ°νκΈ°! (μ΄κΈ°νν λ)
const new_array = Array.from({length:4})κΉμ§λ§ νλ©΄
[undefined,undefined,undefined,undefined]
const new_array = Array.from({length:4) , (item, idx)
=>{return idx;});
[0,1,2,3]
γ γ γ νΌμμν°><