JS Basic: By Value V.S By Reference

Leeboy @ goodideas-studio2017.03.10

Primitive type(1/6)

Booleans

Number

String

undefined

null

compare by value ⽤值相比

只有在具有相同的值，兩者才相等

Pass by value (e.g 1)

Copy by value (e.g 2)

Primitive type(2/6)e.g.1 Pass by value

Primitive type(3/6)e.g.2 Copy by value

Primitive type(4/6)String

- 不可變的（immutable）(e.g 3)

- 長度相等，索引位置字元相等 👉Quiz

- Are strings compared by value or by reference?

Primitive type(5/6)immutable

Quiz1Q:寫⼀個比較兩字串的函數

Primitive type(6/6)summary

Objective type(1/4)

Object

Function

Array

Set

mutable

compare (e.g1)(e.g 2)

個別物件永不相等

個別陣列永不相等

clone 如何複製 (e.g3)(👉quiz)

Objective type(2/4)e.g.1 Compare by reference

Two references to distinct values are not equal, even if the two values consist of the same bytes.

Objective type(3/4)e.g.2 Compare by reference

Two references are compared to see if they refer to the same value.

Objective type(4/4)e.g.3 Object Clone

Quiz2 Array Clone

請複製 const DC = ['Batman', 'Jocker', 'Flash', 'SuperGirl']

DC_copy.push(‘Arrow') //在複製的陣列 push ⼀個新值

console.log(DC,DC_copy) // 印在 console