js的6道基础题（笔试常考题）

转载：http://www.bubuko.com/infodetail-20477.html

题目一：找出数字数组中最大的元素

var arr=[0,1,2,3,4,5,6,7,8,9];console.log(Math.max.apply(null,arr))

题目二：转化一个数字数组为function数组（每个function都弹出相应的数字）

for循环闭包的问题

var arr=[0,1,2,3,4,5,6,7,8,9],arrFunc = [];for(var i = 0, l = arr.length; i < l; i++){  arrFunc.push((function(i) {    return function() {      console.log(arr[i]);    }  })(i))}

题目三：给object数组进行排序（排序条件是每个元素对象的属性个数）

Object.prototype.myLength = function(){  var length = 0;  for(var i in this){    length ++;  }  return length;}var objArr = [  {a:1, b:2, c:5, d:7, e:8, g:0, h:12, i:5, v:9, w:9, x:9, y:9, z: 15},  {a:2, b:2, c:5, d:7, e:8, g:0, h:12, i:5, j:7, k:5, l:9, m:9, n:0, o:1, p:9, x:9, y:9, z:9 },   {a:3, b:2, c:5, d:7, e:8, g:0, h:12, i:5, j:7, k:5, l:9, m:9, n:0, o:1, p:9, q:0 },  {a:4, b:2, c:5, d:7, e:8, g:0, h:12, i:5, j:7, k:5, w:9, x:9, y:9, z:9 },  {a:5, b:2, c:5, d:7, e:8, g:0, h:12, i:5, j:7, k:5, v:9, w:9, x:9, y:9, z:9 },  {a:6, b:2, c:5, d:7, e:8, g:0, h:12, i:5, j:7, k:5, l:9, m:9, n:0, o:1, p:9, q:0, r:8, s:9, t:9, z:9 },  {a:7, b:2, c:5, d:7, e:8, x:9, y:9, z:9 }];// arr before sortvar numArr1 = []for(var i = 0, l = objArr.length; i < l; i++ ){  numArr1.push( objArr[i].myLength() )}console.log(numArr1.join(" ")) //result// arr after sortobjArr.sort(function(a,b){  // stable sort  // return (a.myLength() > b.myLength()) === true? 1:-1;  // unstable sort  return (a.myLength() >= b.myLength()) === true? 1:-1;  // return a.myLength() - b.myLength();})var numArr2 = []for(var i = 0, l = objArr.length; i < l; i++ ){  // console.log(i,l,objArr[i].myLength());  numArr2.push( objArr[i].myLength() )}console.log(numArr2.join(" ")) //result

题目四：利用JavaScript打印出Fibonacci数（不使用全局变量）

var fibonacci = (function(){  var s = [];  var fun = function(x) {    if(s[x]){      return s[x];    }    if(x < 0) {      throw "Can‘t be negative";      return ;    }    else if(x === 0 || x === 1) {      s[x] = s[x] || x;      return s[x];    }    else{      s[x] = ( fun(x - 1) + fun(x - 2) );      return s[x];    }  };  fun.print = function() {    console.log(s.join(" "));  }  fun.printLast = function() {    // console.log(s.length);    return(s[s.length-1]);  }  window.s = s;  return fun;})()console.time(200);console.log(fibonacci(200));console.log(fibonacci.printLast());console.log(fibonacci.print());console.timeEnd(200);

var fibonacci2 = function(x){  if(x < 0) {    throw "Can‘t be negative";    return ;  }  if(x === 0 || x === 1) {    return x;  }  var num = ( fibonacci2(x - 1) + fibonacci2(x - 2) )  return num;}console.time(32);console.log(fibonacci2(32));console.timeEnd(32);

题目五：实现如下语法的功能：var a = (5).plus(3).minus(6);

Number.prototype.plus = function(x) {  var num = this.valueOf() + x;  return Number(num);}Number.prototype.minus = function(x) {  var num = this.valueOf() - x;  return Number(num);}var a = (5).plus(3).minus(6);console.log(a);alert(a);

题目六：实现如下语法的功能：var a = add(2)(3)(4);

function add(x) {  var mid;  mid = x || 0;  function addObj(x) {    x = x || 0;    mid = mid + x;    return addObj;  }  addObj.valueOf = function() {    return mid;  }  addObj.toString = function() {    return mid;  }  return addObj;}//call the obj.valueOf functionconsole.log(add(2));console.log(add(2)(3));console.log(add(2)(3)(4));console.log(add(2)(3)(4)(5));//call the obj.toString functionalert(add(2));alert(add(2)(3));alert(add(2)(3)(4));alert(add(2)(3)(4)(5));