常见面试题手动整理

1. 宽度百分比 不用高度画正方形

2. 不知宽高水平垂直居中

3. 封装一个方法返回字符串长度(汉字为2位)

4. antd-layout-ui 写个方法变成驼峰

5. [] === ![]

6. 输出结果?

    function fn(a) {
        console.log(a);
        var a = 123;
        console.log(a);
        function a() { }

        console.log(a);
        console.log(b);
        var b = function () { }
        console.log(b);
    }
    fn(1);

7. 输出结果?

    a = 100;
    function deme(e) {
        function a() { }
        arguments[0] = 2;
        console.log(e);
        if (a) {
            var b = 123;
            var c = function () { }
        }
        var c;
        a = 10;
        var a;
        console.log(b);
        f = 123;
        console.log(c);
        console.log(a);
    }

    var a;
    deme(1);
    console.log(a);
    console.log(f);

8. 输出结果?

    function fonn(x) {
        console.log(arguments);
        return x
    }
    fonn(1, 2, 3, 4, 5);

9. 输出结果?

    function fonn(x) {
        console.log(arguments);
        return x
    } ()

10. 输出结果

    ! function fu() {
        console.log("执行");

    }();

11. 输出结果?

    function fonn(x) {
        console.log(arguments);
        return x
    } (1, 2, 3, 4, 5)

12. 输出结果?

    var p1 = new Person();
    p1.say();
    p1.say();

    var p2 = new Person();
    p2.say();

13. 输出结果?

    var x = 1; y = z = 0;
    function add(n) {
        return n = n + 1;
    }
    y = add(x);
    function add(n) {
        return n = n + 3;
    }
    z = add(x);
    console.log(x, y, z);

14. 输出结果

    var str = 'abc';
    str += 1;
    var test = typeof str; //string
    if (test.length == 6) {
        test.sign = "xyz"
    }
    console.log(test.sign);

15. 分别输出什么?

    function Person(name, height) {
        this.name = name;
        this.height = height;
        this.say = function () {
            console.log(this.name);
        }
        // 不返回
        //return this
        //return {}
        //return 123
    }

    var per1 = new Person('小王', 175);
    //分别打印什么
    console.log(per1.name);

16. 打印什么?

    Teacher.prototype.name = "ABBB";
    function Teacher() {

    }

    var tea1 = new Teacher();
    Teacher.prototype = {
        name: "CDDDD"
    }

    console.log(tea1.name);

17. 打印什么?

    Teacher.prototype.name = "ABBB";
    function Teacher() {

    }

    Teacher.prototype = {
        name: "CDDDD"
    }

    var tea1 = new Teacher();

    console.log(tea1.name);

18. 页面显示什么

    var obj = { name: "sum" };
    var obj1 = Object.create(obj);
    var ong = Object.create(null)

    document.write(obj1)
    document.write(ong)

19. 手写找出 body里面的 p 元素,并打印对应的索引

20. 输出结果

    let fn = function () {
        let num = 1; //自由变量
        return {
            a: function () {
                console.log(num);
            },
            b: function () {
                num++;
            }
        };
    };


    let closure = fn();
    fn = null;
    closure.a();