[TOC] #### 箭頭函數 如果參數只有一個,可以不用加傳參的小括號 如果函數內容只有一行,可以不用加花括號和return,會直接返回=>后面的結果 let pf = x=>x*x; let foo = (x,y)=>x+y; let foo = (x,y)=>{ x++; y++; return x*y; } document.write(foo(3,4)); #### 設置默認值 let foo = (x,y=1)=>{ return x*y; } document.write(foo(4)); #### 神奇的三點 1.如果...arr當做形參，功能就是用來接收多余的參數 let foo = (x,y,...arr)=>{ //hd是一個數組,存放多傳入的參數 console.log(arr); }; foo(1,2,'a','b','c') 2.如果...arr寫在實參中,就表示將arr拆散 let foo = (x,y,z)=>{ return x*y*z; } let arr = [3,4,5]; document.write(foo(...arr)); let arr = [4,5]; document.write(foo(3,...arr)); #### 解構賦值 1.數組的解構賦值 let [hd,url] = ['后盾人','www.houdunren.com']; console.log(hd); console.log(url); 2.解構賦值就是"模式匹配",說白了,只要是左右兩邊結構一樣,就能一一對應 let [x,[[y],[[z]]],q] = [1,[[2],[[3]]],4]; console.log(x); console.log(y); console.log(z); console.log(q); eg:值的互換 <script type="text/javascript"> var x = 1; var y = 2; //var z = x; //x = y; //y = z; let [x,y] = [y,x]; console.log(x); console.log(y); </script> #### 對象的解構賦值 對象的解構賦值,左右兩邊的變量名要一樣,和對象中變量的順序沒有關系 <script type="text/javascript"> //let {hd,url} = {hd:'后盾人',url:'www.houdunren.com'}; //let {hd,url} = {url:'www.houdunren.com',hd:'后盾人',year:'2018'}; //結構并且重命名 let {hd:h,url:u} = {url:'www.houdunren.com',hd:'后盾人',year:'2018'}; console.log(h); console.log(u); </script> #### 字符串的解構賦值 let [x,y] = [1,2]; console.log(x,y); //let [x,y,z] = '后盾人'; console.log(x); console.log(y); console.log(z); //x、y、z分別對應后、盾、人 let {length:l} = '后盾人'; console.log(l); 運行結果：3 #### 函數參數的解構賦值 function foo([x,[[y]]]){ return x*y; } document.write(foo([3,[[4]]]));