机试

1.todolist

<input type="text" id="input">
<ul id="app">
</ul>
<script>
  var arr = []
  var input = document.getElementById("input")
  var app = document.getElementById("app")
  input.onkeydown = function(event){
    if(event.keyCode == 13){
      if(arr.indexOf(this.value) == -1 && this.value!=""){
        arr.push(this.value)
        var li = document.createElement("li")
        li.innerHTML = this.value
        app.append(li)
      }
      console.log(arr);
    }
  }
</script>

2.tab切换

<ul>
  <li class="current">html</li>
  <li>css</li>
</ul>
<div class="parent">
  <div class="html">html</div>
  <div class="css">css</div>
</div>
    <script>
        var lis = document.getElementsByTagName("li")
        var divs = document.querySelectorAll(".parent div")
        for(let i=0;i<lis.length;i++){
            lis[i].index = i;
            lis[i].onclick = function(){
                for(let i=0;i<lis.length;i++){
                    lis[i].classList.remove("current")
                }
                this.classList.add("current")
                for(let i=0;i<divs.length;i++){
                    divs[i].style.display = "none"
                }
               divs[this.index].style.display = "block"
            }
        }
    </script>

3.取最大值 && 求和

var arr = [10,22,14,4];

取最大值 (写两种方法)

var arr = [10,22,14,4]
/ 取最大值 /
//1.算法实现
var maxNum = arr[0]
for(var i=1;i<arr.length;i++){
if(maxNum<arr[i]){
maxNum = arr[i]
}
}
console.log(maxNum);
// 2.数组方法实现
console.log(Math.max(...arr));

求和(写两种方法)

/ 求和 /
var sum =0;
for(var i=0;i<arr.length;i++){
    sum+=arr[i]
}
console.log(sum);
var s = arr.reduce((a,b)=>{
return a+b
})
console.log(s);

4.根据count值升序

var obj  = [
  {name:"cheng",count:30},
  {name:"li",count:12},
  {name:"zhang",count:14}
];
var res=obj.sort((a,b)=>{
            return a["count"]-b["count"]
})
console.log(res)

5.数据处理

var obj =[
{
"isSelected": true,
"name": "纸上行舟",
"count": 3,
"id": "0001"
},
{
"isSelected": true,
"name": "我可能得抑郁症了！舟",
"count": 2,
"id": "0002"
},
{
"isSelected": true,
"name": "绕日飞行",
"count" : 4,
"id": "0003"
}
]
var res = []
for(var i=0;i<obj.length;i++){
var {id,name} = obj[i]
res.push({
        id,
        name
    })
}
console.log(res);

6.输入框,获取对应的数据

<script>
    var arr = [
        {name:"你是谁,他在那里",id:1102},
        {name:"圈住你在那里",id:1102},
        {name:"hello在那里",id:1102},
        {name:"怪你哈哈",id:1102},
        {name:"world",id:1102},
    ]
    /* 1.enter回车获取关键字
    2.使用关键字,对数据查询,得到一个新的数组
    3.name的字符超过3位以...结尾
    */
    var txt = document.getElementById("txt")
    txt.onkeydown = function(event){
        if(event.keyCode == 13){
            var value = this.value
            if(value){
                var res = arr.filter(item=>{
                    return item["name"].includes(value)
                })
                res.map(item=>{
                    if(item.name.length>3){
                        return item.name = item.name.slice(0,3)+"..."
                    }
                })
                console.log(res);
            }
        }
    }