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javascript basic algorithm summary

  • 2021-01-25 07:02:56
  • OfStack

In this paper, we share five javascript algorithms for your reference, the specific content is as follows

1. Linear lookup 


<!doctype html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title> Linear search </title>
</head>
<body>

 <p> The array is: [2,4,6,23,53,545,65,3,24,5,3,6]</p>
 <p> Enter the value to look up :<input type="text" id="serch" onchange="search_index(this.value)"><p>
 <p> The value in the array position is: <span id="val"></span><p>



 <script>   
  //1. Declare the lookup function 
  //Arr For arrays, x Is the value to search for 
   function search(Arr,x){
    for(var i=0; i<Arr.length; i++){
     if(Arr[i]==x){
      return i; // return x Position in the array; 
     }
    }
    return " There is no "; // The end of the loop has not been discovered   It returns " There is no ";
   }
  
   //2. Examples of practice 
   var arr=[2,4,6,23,53,545,65,3,24,5,3,6]; // The statement 1 An array   
   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(" The loop executes :");
    for(var i=0; i<Arr.length;i++){
     count++
     console.log(count);// The number of times the output loop is executed 
     if(Arr[i]==x){
      return i;
     }
    }
    return " The value does not exist ";
   }  
     
  
 </script>
</body>
</html>

2.2 points to find 


<!doctype html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>2 Look up the temperature </title>
</head>
<body>
 
 <script>
 //2 The fractional lookup value applies to an already sorted array 
 //2 Divide is to find the middle   Fewer steps 
 var arr=[-13,2,4,6,8,12,34,35,45,56,57,88,110,234,239,342];// Orderly array 
 
 function binarySearch(arr,x){
  var low=0,high=arr.length-1;
  var count=0;
  while(low<=high){
   count++;
   console.log(" This is the first "+count+" loops ");
   var mid=Math.floor((low+high)/2);
   if(arr[mid]==x){
    console.log("x The guide in the array is :"+mid);
    return mid;
   }
   if(arr[mid]<x){// If the value you're looking for is greater than 2 Score is low=mid+1 ; 

    low=mid+1;
    console.log(" At this time low The value is :"+low);
   }else{
    high=mid-1;// If the value you're looking for is less than 2 Score is high=mid-1 ; 
    console.log(" At this time high Values are: "+high);
   }

  }

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

Bubble Sort 


<!doctype html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>javascript Bubble sort </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;// The statement 1 Cache variables 
   var count_outer=0;// Outer cycle count 
   var count_inner=0;// Inner cycle count 

   for(var i=0; i<arr.length;i++){// The first 1 Layer circulation 
    count_outer++;
    console.log(" This is the fourth part of the outer cycle "+count_outer+" time ");
    for(var j=arr.length;j>0;j--){// The first 2 Layer circulation 
     count_inner++;
     console.log("................... This is the first part of the inner cycle "+count_inner+" time ");
     if(arr[j-1]<arr[j-2]){// Behind the judgment 1 If the value is less than the previous value 1 value 
      temp=arr[j-2];// So store the previous values temp inside 
      arr[j-2]=arr[j-1];// And then I'm going to put 1 Straight on the front face value 
      arr[j-1]=temp;// In the temp I put the value in the back there 
     }
     console.log("....................................... Outer layer of the first "+count_outer+" loops "+" The inner layer first "+count_inner+" loops "+" The result of sorting the array is "+arr)
    }
   }
   return " The final sorted array is :["+arr+"]....1 The total cycle "+count_inner+" time ";

  }
  
console.log(bubbleSort()); // Console output 

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

4. The factorial 


<!doctype html>
<html>
<head>
 <meta charset="UTF-8">
 <title> factorial </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  is 1 An array of objects   Contains the arguments passed in the function   He has a 1 A property callee, It is a 1 A pointer to the   Point to have this arguments The function of the object is just factorial
   }
  }

  var fac=factorial;// The function name without parentheses is 1 A pointer to the function   all fac And now it's also pointing to this factorial function 
  alert(fac(3));//6

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

5. Output odd-even control 


<html>
 <head>
  <title> Only odd or even entries are printed </title>
 </head>
 <body>
  <script>
  var ck = true;// The global variable 
  function oddOreven(num) { //num for 0 or 1  Control output   Is it an odd number or an even number 
   for (var i = 0; i < 30; i++) {
    if (ck) {
     ck = false; // if ck for true  Let it is equal to the false
     alert(i + num);
    } else {
     ck = true;
    }
   }
  }
  // call 
  oddOreven(0); // An even number 
  oddOreven(1) // An odd number 
  </script>
 </body>
</html>

The above is all the content of this article, I hope to help you better learn javascript programming.

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