// 箭头函数
// this指向定义时所在的对象，而不是调用时所在的对象
// 不可以作为构造函数
// 不可以使用arguments对象
function sum(x, y) {
return x + y
}
console.log(sum(3, 5))
let sum = function (x, y) {
return x + y
}
let sum = (x, y) => {
console.log(this) // 这里的this就是window
return x + y
}
console.log(sum(1, 2))
let name = "Yang"
let age = 19
let s = "school"
let obj = {
name,
age,
[s]: "阆中中学", //属性名是一个变量需要用[]来表示
study() {
console.log(this)
console.log(this.name + "正在学习")
}
}
obj.study()
console.log(Object.is(NaN,NaN)) // true
console.log(Object.is(-1, 1))
let obj1 = {
name: "Yang",
age : 19
}
let obj2 = {
name: "Yang",
age : 19
}
console.log(Object.is(obj1, obj2)) //这里面不相等，主要是值相等，但是地址不相等。js中对象的是引用数据类型。
let x = {
a:3,
b:4
}
console.log({...x}) //重点
let y = {...x} //对象的扩展运算符
console.log(y)
console.log(Object.is(x, y))
let z = {
c: 7,
a: 6
}
Object.assign(x,z) //对象的合并
console.log(x)
console.log("a" in x) //true a这个属性值在x里面
let arr = [1, 2, 3]
console.log(3 in arr) //false 这里面是判断小标为3的里面有没有值
let obj3 = {
name: "Yang",
age : 19,
[s] : "四川师范大学成都学院-四川工商学院"
}
for(let key in obj3){
console.log(key) // 属性
console.log(obj3[key]) //值
}
Object.keys(obj3).forEach((item,index) => {
console.log(item) //name age school
console.log(index) //0, 1, 3
})
Object.getOwnPropertyNames(obj3).forEach(key => {
console.log(key, obj3[key])
})
Reflect.ownKeys(obj3).forEach(key => {
console.log(key, obj3[key])
})
let target = {
a: {
b: {
c: 1,
d: 2
},
e: 2,
f: 3,
g: 4
}
}
let source = {
a: {
b: {
c: 1
},
e: 2,
f: 3
}
}
Object.assign(target, source)
console.log(target)
let a = 5
let b = a
a = 6
console.log(a, b) //这是深拷贝
let obja = {
name: "严钢",
age: 18
}
obja.age = 24
// let objb = obja //这里面就是浅拷贝 这里面 obja objb指向同一个内存地址
//console.log(objb)
console.log(obja)
// JSON.stringify() //把一个对象转化为JSON字符串
// JSON.parse() //把一个JSON字符串转换为一个对象
let str = JSON.stringify(obja)
let objb = JSON.parse(str)
console.log(objb)
let checkType = data => {
return Object.prototype.toString.call(data).slice(8, -1) //判断类型
}
let deepClone = target =>{
let targetType = checkType(target);
let result
if ( targetType === "Object"){
result = {}
}else if(targetType === "Array"){
result = []
}else {
return target
}
for (let i in target){
let value = target[i]
let valueType = checkType(value)
if(valueType === "Object" || valueType === "Array"){
result[i] = deepClone(value)
}else{
result[i] = value
}
}
return result
}
let arr1 = [1, 2, {age: 18},["codeing", "sleeping"]]
let arr2 = deepClone(arr1)
arr2[2].age = 34
arr2[3][1] = "严钢我来自地球"
console.log(arr1, arr2)
一起设计吧
