递归思想js实现

2018/05/29 20:46
阅读数 0

熟悉递归的同学就不用再解释什么递归了。

直接来练习递归

题目一求1-10的和


function sum(n) {
if(n===1){
return 1;
}
return sum(n-1)+n;
}

题目二求阶乘问题比如1*2*3…*5


function multiple(n) {
if(n===1){
return 1;
}
return multiple(n-1)*n;
};
console.log(multiple(5));

最著名的斐波那契列数列


function fibonacci(n){
if(n <= 2){
return 1;
}
return fibonacci(n-1) + fibonacci(n-2);
}

console.log(fibonacci(10));

利用递归遍历所有的后代元素

方法1

window.onload = function () {
//给页面中所有的元素添加一个边框 1px solid pink
//DOM中,没有提供直接获取后代元素的API
//但是可以通过childNodes来获取所有的子节点

//先找body的所有子元素
//再找body的子元素的所有子元素
function getChildNode(node) {
var allNode=node.childNodes;

for (var i = 0; i < allNode.length; i++) {
var current=allNode[i];
if(current.nodeType===1){
current.style.border="1px red solid";
getChildNode(current);
}
}
}
getChildNode(document.body);
}

//方法1改进(1)

var allNodeArr=[];//改进的地方

function getChildNode(node) {
var allNode=node.childNodes;
for (var i = 0; i < allNode.length; i++) {
var current=allNode[i];
if(current.nodeType===1){
allNodeArr.push(current);//改进的地方
getChildNode(current);
}
}
}
getChildNode(document.body);
for (var i = 0; i < allChildren.length; i++) {
var child = allChildren[i];
child.style.border= "1px solid pink";
}

//方法1改进(2)

function getChildNode(node){
//先找子元素
var nodeList = node.childNodes;
var result = [];
//在用子元素再找子元素 这里就可以递归了
//for循环中的条件,就充当了结束的条件
for (var i = 0; i < nodeList.length; i++) {
//childNode获取到到的节点包含了各种类型的节点
//但是我们只需要元素节点 通过nodeType去判断当前的这个节点是不是元素节点
var childNode = nodeList[i];
//判断是否是元素节点
if(childNode.nodeType == 1){
result.push(childNode);
var temp = getChildNode(childNode);
result = result.concat(temp);
}

}
return result;
}

//html代码
<div>1div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>2div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>3div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>4div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>5div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>6div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>7div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>8div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>9div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<div>10div
<p>1p<span>1span</span><span>2span</span><span>3span</span></p>
<p>2p<span>1span</span><span>2span</span><span>3span</span></p>
<p>3p<span>1span</span><span>2span</span><span>3span</span></p>
<p>4p<span>1span</span><span>2span</span><span>3span</span></p>
<p>5p<span>1span</span><span>2span</span><span>3span</span></p>
</div>
<p>我是第1个p标签</p>
<p>我是第2个p标签</p>
<p>我是第3个p标签</p>
<p>我是第4个p标签</p>
<p>我是第5个p标签</p>
<p>我是第6个p标签</p>
<p>我是第7个p标签</p>
<p>我是第8个p标签</p>
<p>我是第9个p标签</p>
<p>我是第10个p标签</p>

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