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Summary of basic javascript algorithms_javascript skills

WBOYOriginal: 2016-05-16 15:11:172438browse

This article shares five javascript algorithms for your reference. The specific content is as follows

1. Linear search

<!doctype html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>线性查找</title>
</head>
<body>

 <p>数组为：[2,4,6,23,53,545,65,3,24,5,3,6]</p>
 <p>输入要查的值:<input type="text" id="serch" onchange="search_index(this.value)"><p>
 <p>这个值在数组的位置是：<span id="val"></span><p>



 <script>   
  //1.声明查找函数
  //Arr为数组，x为要搜索的值
   function search(Arr,x){
    for(var i=0; i<Arr.length; i++){
     if(Arr[i]==x){
      return i; //返回x在数组中的位置；
     }
    }
    return "不存在"; //循环结束还未发现的话 则返回"不存在";
   }
  
   //2.实例练习
   var arr=[2,4,6,23,53,545,65,3,24,5,3,6]; //声明一个数组  
   function $$(id){
    return document.getElementById(id);
   }

  function search_index(value){
    var val=getX(arr,value)
    $$("val").innerHTML=val;
  }

   function getX(Arr,x){
    var count=0;
    console.log("循环执行了:");
    for(var i=0; i<Arr.length;i++){
     count++
     console.log(count);//输出循环执行的次数
     if(Arr[i]==x){
      return i;
     }
    }
    return "该值不存在";
   }  
     
  
 </script>
</body>
</html>

2. Binary search

<!doctype html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>二分查找温故</title>
</head>
<body>
 
 <script>
 //二分查找值适用于已经排好序的数组中
 //二分就是逢中查找 步骤较少
 var arr=[-13,2,4,6,8,12,34,35,45,56,57,88,110,234,239,342];//有序数组
 
 function binarySearch(arr,x){
  var low=0,high=arr.length-1;
  var count=0;
  while(low<=high){
   count++;
   console.log("这是第"+count+"次循环");
   var mid=Math.floor((low+high)/2);
   if(arr[mid]==x){
    console.log("x所在数组内的引索是:"+mid);
    return mid;
   }
   if(arr[mid]<x){//如果要查找的值大于二分值则low=mid+1；

    low=mid+1;
    console.log("此时low的值是:"+low);
   }else{
    high=mid-1;//如果要查找的值小于二分值则high=mid-1；
    console.log("此时high的值是："+high);
   }

  }

 }
binarySearch(arr,45);
 </script>
</body>
</html>

3. Bubble sort

<!doctype html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>javascript冒泡排序</title>
</head>
<body>
 <script>
  var arr=new Array(34,-3,43,67,12,44,21,34,5,645,64,3,43,23,25);

  function bubbleSort(){
   var temp;//声明一个缓存变量
   var count_outer=0;//外层循环计数
   var count_inner=0;//内层循环计数

   for(var i=0; i<arr.length;i++){//第一层循环
    count_outer++;
    console.log("这是外层循环的第"+count_outer+"次");
    for(var j=arr.length;j>0;j--){//第二层循环
     count_inner++;
     console.log("...................这是内层循环的第"+count_inner+"次");
     if(arr[j-1]<arr[j-2]){//判断后面一值如果小于前面一值
      temp=arr[j-2];//那么将前面的值存放在temp里面
      arr[j-2]=arr[j-1];//然后将后面一直放在前面值的位置
      arr[j-1]=temp;//在把temp里的值放在后面那个位置
     }
     console.log(".......................................外层第"+count_outer+"次循环"+"内层第"+count_inner+"次循环"+"后的数组排序结果是"+arr)
    }
   }
   return "最终排序后的数组是:["+arr+"]....一共循环了"+count_inner+"次";

  }
  
console.log(bubbleSort()); //控制台输出

 </script>
</body>
</html>

4. Factorial

<!doctype html>
<html>
<head>
 <meta charset="UTF-8">
 <title>阶乘</title>
</head>
<body>
 <script>
 //created in 2014-04-30 
 //factorial function

  function factorial(num){
   if(num<=1){
    return 1;
   }else{
    return num*arguments.callee(num-1);//arguments 是一个类似数组的对象 包含函数中传入的参数 他有一个属性callee,它是一个指针 指向拥有这个arguments对象的函数也就是factorial
   }
  }

  var fac=factorial;//不带括号的函数名是一个指向该函数的指针 所有fac现在也指向这个阶乘函数
  alert(fac(3));//6

 </script>
</body>
</html>

5. Output odd and even number control

<html>
 <head>
  <title>只输出奇数或者偶数项</title>
 </head>
 <body>
  <script>
  var ck = true;//全局变量
  function oddOreven(num) { //num为0或1 控制输出结果 是奇数还是偶数
   for (var i = 0; i < 30; i++) {
    if (ck) {
     ck = false; //如果ck为true 让其等于false
     alert(i + num);
    } else {
     ck = true;
    }
   }
  }
  //调用
  oddOreven(0); //偶数
  oddOreven(1) //奇数
  </script>
 </body>
</html>

The above is the entire content of this article. I hope it can help everyone learn javascript programming better.

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