範例程式：https://codepen.io/effytseng/pen/WYXKvz Both results mostly are same. So, what kind of scenarios we want to use them? And which one is best for performance?

1. spread operator
vs
array.concat()
effy tseng 2018/11/07

2. 一些廢話01
02
Performance04
Agenda
What is the difference?03
Spread syntax?
Array.prototype.concat()?

3. During our project...

4. During our project...

5. Spread syntax
一. 展開運算符(Spread Operator)是把一個陣列展開成個別值。最常見的是用來組合(連接)陣列。
對應的 ES5 陣列方法是 concat()
https://codepen.io/
二. 陣列的淺拷貝。陣列的淺拷貝有很多方式，這是目前語法上最簡單的一種。
三. 也可以用來把陣列展開，然後傳入函式裡面，當成傳入的參數值。
對應的 ES5 語法是 apply()

6. Spread syntax
五. 物件的淺拷貝 (stage 4)，對應的 ES6 語法是 Object.assign()
四. 把可迭代 (iterable) 或與陣列相似 (Array-like) 的物件轉變為陣列。
可迭代物件有：String、Array、Map 與 Set 物件。
與陣列相似的物件有：函式中的參數物件 "arguments"

7. Array.prototype.concat()
用來合併兩個或多個陣列。此方法不會改變現有的陣列，回傳一個包含 "呼叫者本身值" 的一個新陣列。
語法：var new_array = old_array.concat(value1[, value2[, ...[, valueN]]])

8. What is the difference?
恩...請看範例 XD

9. Conclusion
concat and spreads are very different when the argument is not an array.
When the argument is not an array, concat "arrayifies" it (i.e. converts x to [x]) and proceeds with this
temporary array, while ... tries to iterate it and fails if it can't
To sum it up, when your arguments are possibly non-arrays,
the choice between concat and ... depends on whether you want them to be iterated.

10. Performance
恩...請看範例 XD
Performance-wise concat is much faster, probably because it can benefit from array-specific
optimizations, while ... has to conform to the iteration protocol

11. Thank You