ES6 一些特性
# 解構 const nums = [1,2,3]; const first = nums[0]; const second = nums[1]; 可以改用 const [first, second] = nums; # 要只取第二個 const [, second] = nums; # 預設值 # 原本 fourth 應該是 undefined, 但透過後面的 assign 給定預設值 const [, second, third, fourth = 0] = nums; # 值交換 let a = 1; let b = 2; [a, b] = [b, a]; # 剩餘部分 const nums = [1,2,3,4]; const [first, ...other] = nums; # nums => [2,3,4] # 物件解構 const points = {x:1,y:2}; # x = 1 const {x} = points; # rename x to px (只限定物件, 不可以用在Array) const {x:px} = points; Expression 表達式 Statement 陳述式 Expression => 可以用 ()包起來的 Statement => 無法用()包起來的 ex: if (1>2) 表達式 1+2; const a; a+2; 字串模板 字串模板內可以放入表達式 function greet(name, days) { console.log(`Hello, ${name}! It has been ${days * 24} hours not seen you!`); } # or function greet(name, days) { console.log(`Hello, ${name}! ${(days < 7) ? '' : 'Long time no see'}`); } 字串模板也支援多行字串 const str = ` 123456 12345 1234567 `; arrow function 內的 this 會