1.引用類(lèi)型有哪些均抽?非引用類(lèi)型有哪些
引用類(lèi)型:對(duì)象嫁赏、數(shù)組、函數(shù)油挥、正則潦蝇;引用類(lèi)型是指那些保存在堆內(nèi)存的對(duì)象
非引用類(lèi)型:數(shù)值、布爾值深寥、null攘乒、underfind;指保存在棧內(nèi)存中的簡(jiǎn)單數(shù)據(jù)
2.如下代碼輸出什么惋鹅?為什么
var obj1 = {a:1, b:2};
var obj2 = {a:1, b:2};
console.log(obj1 == obj2); //false,obj1和obj2指向存儲(chǔ)在堆內(nèi)存中兩個(gè)不同的地址
console.log(obj1 = obj2); //{a:1,b:2},賦值后obj1和obj2指向同一個(gè)對(duì)象{a:1,b:2}
console.log(obj1 == obj2); //true,賦值后兩個(gè)變量指向同一個(gè)對(duì)象
3.如下代碼輸出什么? 為什么
var a = 1
var b = 2
var c = { name: '饑人谷', age: 2 }
var d = [a, b, c]
var aa = a
var bb = b
var cc = c
var dd = d
a = 11
b = 22
c.name = 'hello'
d[2]['age'] = 3
console.log(aa) //1,a的值賦值給aa生成新的位置则酝,完全獨(dú)立,互不影響
console.log(bb) //2负饲,基礎(chǔ)類(lèi)型賦值后堤魁,兩個(gè)變量互不影響
console.log(cc) //{name: 'hello',age: 3},cc和c指向同一個(gè)對(duì)象,c改變返十,cc也會(huì)變
console.log(dd) //[1,2,{name:'hello',age:'2'}],a,b值改變對(duì)dd沒(méi)有影響妥泉,d的值改變dd也會(huì)變
4.如下代碼輸出什么? 為什么
var a = 1
var c = { name: 'jirengu', age: 2 }
function f1(n){
++n
}
function f2(obj){
++obj.age
}
f1(a)
f2(c)
f1(c.age)
console.log(a) //1,f1(a)時(shí)相當(dāng)于var n = a,n的值變了a不變
console.log(c) //{name: '饑人谷',age: 3},把c賦值給obj后,兩個(gè)變量指向相同對(duì)象洞坑,obj值變了盲链,c的值也會(huì)變
5.過(guò)濾如下數(shù)組,只保留正數(shù)迟杂,直接在原數(shù)組上操作
var arr = [3,1,0,-1,-3,2,-5]
function filter(arr){
for (var i = 0; i < arr.length; i++) {
if (arr[i] <= 0) {
arr.splice(i,1); //splice()方法用來(lái)刪除刽沾、插入、替換數(shù)組中的項(xiàng)排拷,并且返回一個(gè)數(shù)組
--i;
}
}
return arr;
}
filter(arr)
console.log(arr) // [3,1,2]
6.過(guò)濾如下數(shù)組侧漓,只保留正數(shù),原數(shù)組不變监氢,生成新數(shù)組
var arr = [3,1,0,-1,-3,2,-5]
function filter(arr){
var arr1=[];
var j = 0;
for (var i = 0; i < arr.length; i++) {
if(arr[i] > 0){
arr1[j] = arr[i];
j = j + 1;
}
}
return arr1;
}
var arr2 = filter(arr)
console.log(arr2) // [3,1,2]
console.log(arr) // [3,1,0,-1,-2,2,-5]
7.寫(xiě)一個(gè)深拷貝函數(shù)布蔗,用兩種方式實(shí)現(xiàn)
var obj = {a:1, b:2};
function deepCopy(obj) {
var newObj = {};
for (var key in obj) {
if(obj.hasOwnProperty(key)){
if(typeof obj[key] == 'number' || typeof obj[key] == 'string' || typeof obj[key] == 'boolen' || obj[key] == null || obj[key] == underfind) {
newObj[key] = obj[key]
}else {
newObj[key] = deepCopy(obj[key])
}
}
return newObj
}
}
var obj2 = deepCopy(obj);
obj.a = 3;
console.log(obj2.a);
//第二個(gè)
var obj = {a:1, b:2};
function deepCopy(obj) {
return JSON.parse(JSON.stringify(obj))
}
deepCopy(obj);
var obj1 = deepCopy(obj);
obj.a = 2;
console.log(obj1.a);