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## JavaScript #### Json数据如下：person = [{name:"甲",dateOfBirth:"1991-01-01",sex:"male"},{name:"乙",dateOfBirth:"1992-01-01",sex:"female"},{name:"丙",dateOfBirth:"1989-08-21",sex:"female"},{name:"丁",dateOfBirth:"1991-06-22",sex:"female"}];，筛选出sex为female的数据。 ``` var person = [{name:"甲",dateOfBirth:"1991-01-01",sex:"male"},{name:"乙",dateOfBirth:"1992-01-01",sex:"female"},{name:"丙",dateOfBirth:"1989-08-21",sex:"female"},{name:"丁",dateOfBirth:"1991-06-22",sex:"female"}]; var girls = person.filter(function(item){ return item.sex =="female"; }) console.log(girls); ``` #### Json数据同上，从筛选出的girls中按照dateOfBirth排序 ``` girls.sort(function(a,b){return a.dateOfBirth>b.dateOfBirth?1:-1;}); console.log(girls); ``` #### 求12589到25689之间的整数，满足各位数字之和为5的倍数的个数。 ``` var count =0; for(var i=12589;i<=25899;i++){ var result=0; var a =i%10; var b =Math.floor((i/10)%10); var c =Math.floor((i/100)%10); var d =Math.floor((i/1000)%10); var e =Math.floor(i/10000); result = a+b+c+d+e; if(result%5==0) count++; } console.log("总数为"+count); ``` #### 请把以下用于连接字符串的JavaScript代码修改为更高效的方式 ``` var htmlString = ‘ < div class=”container” > ’ + ‘ < ul id=”news-list” > ’; for (var i = 0; i < NEWS.length; i++) { htmlString += ‘ < li > < a href=”’ +NEWS[i].LINK + ‘” > +NEWS[i].TITLE + ‘ < /a > < /li > ’; } htmlString += ‘ < /ul > < /div > ’; ``` 分析：考点1-JavaScript的字符串连接机制；考点2-NEWS.length需要缓存，不然每次循环都要重新计算一次length。 ``` var htmlString=[]; htmlString.push(‘ < div class=”container” > ’ + ‘ < ul id=”news-list” > ’); for(var i = 0, len = NEWS.length; i < len; i++){ var news = NEWS[i]; htmlString.push('

  • '+ news.TITLE+'
    • '); } htmlString=htmlString.join(""); ``` #### 尝试实现注释部分的Javascript代码，可在其他任何地方添加更多代码（如不能实现，说明一下不能实现的原因）： ``` var Obj = function(msg){ this.msg = msg; this.shout = function(){ alert(this.msg); } this.waitAndShout = function(){ //隔五秒钟后执行上面的shout方法 } } ``` 解： ``` var Obj = function(msg){ this.msg = msg; this.shout = function(){ alert(this.msg); }; this.waitAndShout = function(){ var that = this; setTimeout(function(){that.shout();},5000); //隔五秒钟后执行上面的shout方法 } return this; } Obj("shouting").waitAndShout(); ``` ps：在[jsbin](http://jsbin.com)中只能显示一次，无法循环，待定。 #### 完成后续代码，计算两个数组的交集，并指出该算法的时间复杂度和空间复杂度。 ``` var arr1=[1,2,3,3,4,2,3,5]; var arr2=[3,4,4,3,5,7,8]; var arr3=[]; //计算arr1å’Œarr2两个数组的交集，将结果保存到arr3中 console.log(arr3); ``` 解： ``` var arr1=[1,2,3,3,4,2,3,5]; var arr2=[3,4,4,3,5,7,8]; var arr3=[]; var len1=arr1.length,len2=arr2.length; for(var i=0;i