The document discusses the differences between passing values by value versus by reference in JavaScript. It explains that primitive types like numbers and strings are compared by value, so two primitive values are equal only if they have the same value. In contrast, object types like arrays and objects are compared by reference, so two object references are equal only if they refer to the same object. The document provides examples of comparing values and references, as well as cloning objects to make copies. It also includes two quizzes, one to write a function to compare two strings, and another to clone an array value.

1. JS Basic:
By Value V.S
By Reference
Leeboy @ goodideas-studio
2017.03.10

2. 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)

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

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

5. 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?

6. Primitive type(5/6)
immutable

7. Quiz1
Q:寫⼀個比較兩字串的函數

8. Primitive type(6/6)
summary

9. 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)

10. 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.

11. Objective type(3/4)
e.g.2 Compare by reference
Two references are compared
to see if they refer to the same value.

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

13. 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