Summary of basic javascript algorithms_javascript skills
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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