前端 JS 笔试百题( 六 ) _小知识

下面程序的输出结果是多少？

function sum(a, b) {return a + b;}sum(1, "2");

下面程序的输出结果是多少？

var str = "我非常喜欢编程";str.length = 3;console.log(str);

下面程序的输出结果是多少？

let number = 0;console.log(number++);console.log(++number);console.log(number);

下面程序的输出结果是多少？

function nums(a, b) {if (a > b)console.log('a is bigger')elseconsole.log('b is bigger')return a + b}console.log(nums(4, 2))console.log(nums(1, 2))

下面程序输出结果是多少？

function side(arr) {arr[0] = arr[2];}function func1(a, b, c = 3) {c = 10;side(arguments);console.log(a + b + c);}function func2(a, b, c) {c = 10;side(arguments);console.log(a + b + c);}func1(1, 1, 1);func2(1, 1, 1);

下面代码的输出结果是什么？

var a = 3;var b = new Number(3);var c = 3;console.log(a == b);console.log(a === b);console.log(b === c);

执行下列语句后，a.length的值为？

var a = [];a.push(1, 2);a.shift(3, 4);a.concat([5, 6]);a.splice(0, 1, 2);

下面这几段代码分别输出结果是多少？为什么？

var a = {}, b = '123', c = 123;a[b] = 'b';a[c] = 'c';console.log(a[b]);// example 2var a = {}, b = Symbol('123'), c = Symbol('123');a[b] = 'b';a[c] = 'c';console.log(a[b]);// example 3var a = {}, b = {key:'123'}, c = {key:'456'};a[b] = 'b';a[c] = 'c';console.log(a[b]);

下面每项的返回值是什么？为什么？

null == undefined0.1 + 0.2 == 0.3typeof NaNtypeof Functiontypeof Objecttypeof {}'a' + 1'a' - 1Function instanceof ObjectObject instanceof Function

下面程序的输出结果是多少？

var array = []for(var i = 0; i < 3; i++) {array.push(() => i)}var newArray = array.map(el => el())console.log(newArray)

下面程序的输出结果是多少？

function a(m, n) {var b = function (l) {return l <= m ? l * b(l + 1) : 1;}return b(m - n + 1);}console.log(a(4, 2));

下面程序的输出结果是多少？

console.log(typeof undefined == typeof NULL);console.log(typeof function () {} == typeof class {});

执行后a和b.age的值分别为

var a = 10var b = {age: 11}function fn(x,y) {--y.age;return --x;}fn(a,b)

下面程序的执行结果是：

var number = 4;var numberFactorial = (function (number){return (number === 0)? 1: number* factorial(number-1)})(number)console.log(numberFactorial)

下面程序的输出结果是：

var array = []for(var i = 0; i < 3; i++) {array.push(() => i)}var newArray = array.map(el => el())console.log(newArray)

下面程序的输出结果是：

function addToList(item, list) {return list.push(item)}const result = addToList("nowcoder", ["hello"])console.log(result)

下面程序的输出结果是：

const first = () => { console.log('first'); return false; }const second = () => { console.log('second'); return true; }console.log( first() && second() );console.log( second() || first() );