對於引用類型變量,棧內存中存放的是該對象的訪問地址,在堆內存中爲該值分配空間,因爲這種值的大小不固定,所以不能把他們保存到棧內存中;但內存地址大小是固定的,所以能夠將堆內存地址保存到棧內存中。這樣,當查詢引用類型的變量時,就先從棧中讀取堆內存地址,而後再根據該地址取出對應的值。javascript
引用類型:從一個變量向另外一個新變量複製引用類型的值,其實複製的是指針,最終兩個變量最終都指向同一個對象,會影響到原數據java
let arr1 = [1, {'name': 'a'}]
let shallowClone = (arr) => {
let newArr = []
for (let prop in arr) {
if (arr.hasOwnProperty(prop)) {
newArr[prop] = arr[prop]
}
}
return newArr
}
let arr2 = shallowClone(arr1)
arr2[0] = 2
arr2[1].name = 'b'
console.log(JSON.stringify({arr1})) // {"arr1":[1,{"name":"b"}]}
console.log(JSON.stringify({arr2})) // {"arr2":[2,{"name":"b"}]}
// 基本數據類型未受到影響、引用數據類型仍是受到影響了
複製代碼
let arr1 = [1, {'name': 'a'}]
let arr2 = arr1.concat()
arr2[0] = 2
arr2[1].name = 'b'
console.log(JSON.stringify({arr1})) // {"arr1":[1,{"name":"b"}]}
console.log(JSON.stringify({arr2})) // {"arr1":[2,{"name":"b"}]}
複製代碼
let arr1 = [1, {'name': 'a'}]
let arr2 = arr1.slice()
arr2[0] = 2
arr2[1].name = 'b'
console.log(JSON.stringify({arr1})) // {"arr1":[1,{"name":"b"}]}
console.log(JSON.stringify({arr2})) // {"arr2":[2,{"name":"b"}]}
複製代碼
let obj1 = {
'name': 'k',
'msg': {
'age': '10',
'sex': '男'
},
}
let obj2 = Object.assign({}, obj1)
obj2.name = 'kk'
obj2.msg.age = '20'
console.log(JSON.stringify({obj1})) // {"obj1":{"name":"k","msg":{"age":"20","sex":"男"}}}
console.log(JSON.stringify({obj2})) // {"obj2":{"name":"kk","msg":{"age":"20","sex":"男"}}}
複製代碼
let arr1 = [1, 2, 3, {'name': 'kk'}]
let arr2 = [...arr1]
arr2.push(4);
arr2[3].name = 'kkk'
console.log(JSON.stringify({arr1})) // {"arr1":[1,2,3,{"name":"kkk"}]}
console.log(JSON.stringify({arr2})) // {"arr2":[1,2,3,{"name":"kkk"},4]}
複製代碼
let arr1 = [1, {'name': 'a'}]
// 判斷數據類型
let checkType = (data) => {
return Object.prototype.toString.call(data).slice(8, -1)
}
let deepClone = (data) => {
let newData, targetType = checkType(data)
if (targetType === 'Object') {
newData = {}
}
else if (targetType === 'Array') {
newData = []
}
else {
return data
}
// 遍歷
for (let i in data) {
let val = data[i]
if (checkType(val) === 'Object' || checkType(val) === 'Array') {
newData[i] = deepClone(val)
} else {
newData[i] = val
}
}
return newData
}
let arr2 = deepClone(arr1)
arr2[0] = 2
arr2[1].name = 'b'
console.log(JSON.stringify({arr1})) // {"arr1":[1,{"name":"a"}]}
console.log(JSON.stringify({arr2})) // {"arr2":[2,{"name":"b"}]}
複製代碼
該方法存在侷限性函數