深入理解ES6之数据解构的用法
编程学习 2021-07-04 17:33www.dzhlxh.cn编程入门
本文介绍了深入理解ES6之数据解构的用法，长沙网络推广觉得挺不错的，现在分享给大家，也给大家做个参考。一起跟随长沙网络推广过来看看吧
一 对象解构
对象解构语法在赋值语句的左侧使用了对象字面量
let node = {
type: true,
name: false
}
//既声明又赋值
let {
type,
name
} = node;
//或者先声明再赋值
let type, name
({type,name} = node);
console.log(type);//true
console.log(name);//false
type与name标识符既声明了本地变量，也读取了对象的相应属性值。
解构赋值表达式的值为表达式右侧的值。当解构表达式的右侧的计算结果为null或者undefined时，会抛出错误。
默认值
当你使用解构赋值语句时，如果所指定的本地变量在对象中没有找到同名属性，那么该变量会被赋值为undefined
let node = {
type: true,
name: false
},
type, name, value;
({type,value,name} = node);
console.log(type);//true
console.log(name);//false
console.log(value);//undefined
你可以选择性地定义一个默认值，以便在指定属性不存在时使用该值。
let node = {
type: true,
name: false
},
type, name, value;
({
type,
value = true,
name
} = node);
console.log(type);//true
console.log(name);//false
console.log(value);//true
赋值给不同的本地变量名
let node = {
type: true,
name: false,
value: "dd"
}
let {
type: localType,
name: localName,
value: localValue = "cc"
} = node;
console.log(localType);
console.log(localName);
console.log(localValue);
type:localType这种语法表示要读取名为type的属性，并把它的值存储在变量localType上。该语法与传统对象字面量的语法相反
嵌套的对象结构
let node = {
type: "Identifier",
name: "foo",
loc: {
start: {
line: 1,
column: 1
},
end: {
line: 1,
column: 4
}
}
}
let {
loc: localL,
loc: {
start: localS,
end: localE
}
} = node;
console.log(localL);// start: {line: 1,column: 1},end: {line: 1,column: 4}
console.log(localS);//{line: 1,column: 1}
console.log(localE);//{line: 1,column: 4}
当冒号右侧存在花括号时，表示目标被嵌套在对象的更深一层中（loc: {start: localS,end: localE}）
二 数据解构
数组解构的语法看起来跟对象解构非常相似，只是将对象字面量换成了数组字面量。
let colors = ["red", "blue", "green"]; let [firstC, secondC, thirdC, thursC = "yellow"] = colors; console.log(firstC//red console.log(secondC);//blue console.log(thirdC);//green console.log(thursC);//yellow
你也可以在解构模式中忽略一些项，并只给感兴趣的项提供变量名。
let colors = ["red","green","blue"]; let [,,thirdC] = colors; console.log(thirdC);//blue
thirdC之前的逗号是为数组前面的项提供的占位符。使用这种方法，你就可以轻易从数组任意位置取出值，而无需给其他项提供名称。
解构赋值
let colors = ["red","green","blue"], firstColor = "black", secondColor = "purple"; [firstColor,secondColor] = colors; console.log(firstColor);//red console.log(secondColor);//green
数组解构有一个非常独特的用例，能轻易的互换两个变量的值。
let a =1,b =2; [a,b] = [b,a]; console.log(a);//2 console.log(b);//1
嵌套的解构
let colors = ["red", ["green", "blue"], "yellow"]; let [firstC, [, ssc]] = colors; console.log(ssc);//blue
剩余项
let colors = ["red", "green", "blue"]; let [firstC, ...restC] = colors; console.log(firstC); console.log(...restC); console.log(restC[0]);//green console.log(restC[1]);//blue
使用剩余项可以进行数组克隆
let colors = ["red", "green", "blue"]; let [...restC] = colors; console.log(restC);//["red", "green","blue"]
三 混合解构
let node = {
type: "Identifier",
name: 'foo',
loc: {
start: {
line: 1,
column: 1
},
end: {
line: 1,
column: 4
}
},
range: [0, 3]
}
let {
type,
name: localName,
loc: {
start: {
line: ll
},
end: {
column: col
}
},
range: [, second]
} = node;
console.log(type);//Identifier
console.log(localName);//foo
console.log(ll);//1
console.log(col);//4
console.log(second);//3
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持狼蚁SEO。