妙用ES6新语法,让你的代码更优雅
2019年4月26日解构
解构的作用是可以快速取得数组或对象当中的元素或属性，而无需使用arr[x]或者obj[key]等传统方式进行赋值
数组解构赋值
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var arr = ['1', 2, 3]; //传统方式 var a = arr[0], b = arr[1], c = arr[2]; //解构赋值，是不是简洁很多？ var [a, b, c] = arr; console.log(a);//this is a string console.log(b);//2 console.log(c);//3 |
嵌套数组解构赋值
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var arr = [[1, 2, [3, 4]], 5, 6]; var [[d, e, [f, g]], h, i] = arr; console.log(d);//1 console.log(f);//3 console.log(i);//6 |
函数传数组解构赋值
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var arr = ['this is a string', 2, 3]; function fn1([a, b, c]) { console.log(a); console.log(b); console.log(c); } |
for循环解构赋值
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var arr = [[11, 12], [21, 22], [31, 32]]; for (let [a, b] of arr) { console.log(a); console.log(b); } //11 //12 //21 //22 //31 //32 |
对象解构赋值：
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var obj = { name: 'chris', sex: 'male', age: 26, son: { sonname: '大熊', sonsex: 'male', sonage: 1 } }; var {name, sex, age, son} = obj; console.log(name + ' ' + sex + ' ' + age); //chris male 26 console.log(son); // { sonname: '大熊', sonsex: 'male', sonage: 1 } |
函数传对象解构：
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var obj = { name: 'chris', sex: 'male', age: 26, son: { sonname: '大熊', sonsex: 'male', sonage: 1 } }; function fn2({sex, age, name}) { console.log(name + ' ' + sex + ' ' + age); } fn2(obj); //chris male 26 |
变量名与对象属性名不一致解构：
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var obj = { name: 'chris', sex: 'male', age: 26 }; var {name: nickname, age: howold} = obj; console.log(nickname + ' ' + howold); //chris 26 |
嵌套对象解构：
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var obj = { name: 'chris', sex: 'male', age: 26, son: { sonname: '大熊', sonsex: 'male', sonage: 1 } }; var {name, sex, age, son: {sonname, sonsex, sonage}} = obj; console.log(sonname + ' ' + sonsex + ' ' + sonage); //大熊 male 1 //Babel暂不支持这种嵌套解构 obj = { name: 'chris', sex: 'male', age: [1, 2, 3] } {name, sex, age: [a, b, c]} = obj; console.log(c); |
嵌套对象属性重名，解构时需要更改变量名：
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var obj = { name: 'chris', sex: 'male', age: 26, son: { name: '大熊', sex: 'male', age: 1 } }; //赋值解构 var {name: fathername, son: {name, sex, age}} = obj; console.log(fathername); //chris console.log(name); //大熊 //传参解构 function fn3({sex, age, name, son: {name: sonname}}) { console.log(name + ' ' + sex + ' ' + age + ' ' + sonname); } fn3(obj); //chris male 26 大熊 |
循环解构对象：
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var arr = [{name: 'chris', age: 26}, {name: 'jack', age: 27}, {name: 'peter',age: 28}]; for (let {age, name} of arr) { console.log(name + ' ' + age); } //chris 26 //jack 27 //peter 28 |
解构的特殊应用场景：
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//变量互换 var x = 1, y = 2; var [x, y] = [y, x]; console.log(x); //2 console.log(y); //1 //字符串解构 var str = 'love'; var [a, b, c, d] = str; console.log(a);//l console.log(b);//o console.log(c);//v console.log(d);//e |
扩展运算符
扩展运算符用三个点号表示，功能是把数组或类数组对象展开成一系列用逗号隔开的值
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var foo = function(a, b, c) { console.log(a); console.log(b); console.log(c); } var arr = [1, 2, 3]; //传统写法 foo(arr[0], arr[1], arr[2]); //使用扩展运算符 foo(...arr); //1 //2 //3 |
rest运算符
rest运算符也是三个点号，不过其功能与扩展运算符恰好相反，把逗号隔开的值序列组合成一个数组
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//主要用于不定参数，所以ES6开始可以不再使用arguments对象 var bar = function(...args) { for (let el of args) { console.log(el); } } bar(1, 2, 3, 4); //1 //2 //3 //4 bar = function(a, ...args) { console.log(a); console.log(args); } bar(1, 2, 3, 4); //1 //[ 2, 3, 4 ] |
