js代码大全

"JavaScript代码大全"是一个相对较广泛的主题，因为JavaScript是一种功能强大的编程语言，用于Web开发、应用程序开发和其他许多用途。

1. JavaScript基础示例：

Hello World:

javascript
console.log("Hello, World!");

变量和数据类型:

javascript
var num = 10;
var name = "John";
var isTrue = true;

函数:

javascript
function add(a, b) {
    return a + b;
}

2. DOM操作:

选择元素:

javascript
var element = document.getElementById("myElement");

修改元素内容:

javascript
element.innerHTML = "New content";

事件处理:

javascript
element.addEventListener("click", function() {
    console.log("Element clicked!");
});

3. AJAX和异步请求:

javascript
var xhr = new XMLHttpRequest();
xhr.open("GET", "https://api.example.com/data", true);
xhr.onreadystatechange = function() {
    if (xhr.readyState == 4 && xhr.status == 200) {
        var data = JSON.parse(xhr.responseText);
        console.log(data);
    }
};
xhr.send();

4. jQuery示例:

选择元素:

javascript
$("#myElement").addClass("highlight");

事件处理:

javascript
$("#myButton").click(function() {
    alert("Button clicked!");
});

5. ES6+功能:

箭头函数:

javascript
const add = (a, b) => a + b;

模板字符串:

javascript
const name = "Alice";
console.log(`Hello, ${name}!`);

解构赋值:

javascript
const { firstName, lastName } = person;

6. React示例:

javascript
import React from 'react';

class MyComponent extends React.Component {
    render() {
        return <h1>Hello, World!</h1>;
    }
}

7. Vue示例:

javascript
<template>
  <div>
    <h1>{{ message }}</h1>
  </div>
</template>

<script>
export default {
  data() {
    return {
      message: 'Hello, World!'
    }
  }
}
</script>

8. Node.js示例:

javascript
const http = require('http');

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello, World!\n');
});

server.listen(3000, '127.0.0.1', () => {
  console.log('Server running at http://127.0.0.1:3000/');
});

当涉及到更广泛的JavaScript代码示例时，可以探索

9. 表单验证:

javascript
function validateForm() {
    var name = document.forms["myForm"]["name"].value;
    if (name == "") {
        alert("Name must be filled out");
        return false;
    }
}

10. 数据存储与本地存储:

javascript
// 使用localStorage存储数据
localStorage.setItem('username', 'john_doe');

// 从localStorage检索数据
var username = localStorage.getItem('username');

11. 动画效果与交互:

javascript
// 使用jQuery实现动画效果
$("#myElement").hide(1000).show(1000);

12. 表格操作:

javascript
// 使用JavaScript操作表格
var table = document.getElementById("myTable");
var row = table.insertRow(0);
var cell1 = row.insertCell(0);
cell1.innerHTML = "New cell";

13. 图片轮播:

javascript
var slideIndex = 0;

function showSlides() {
    var slides = document.getElementsByClassName("mySlides");
    for (var i = 0; i < slides.length; i++) {
        slides[i].style.display = "none";
    }
    slideIndex++;
    if (slideIndex > slides.length) {slideIndex = 1}
    slides[slideIndex-1].style.display = "block";
    setTimeout(showSlides, 2000); // Change image every 2 seconds
}

14. 地图集成:

javascript
// 使用Google Maps API显示地图
function initMap() {
    var map = new google.maps.Map(document.getElementById('map'), {
        zoom: 8,
        center: {lat: -34.397, lng: 150.644}
    });
}

15. 用户身份验证:

javascript
// 使用JWT实现用户身份验证
const token = jwt.sign({ userId: user.id }, secretKey, { expiresIn: '1h' });

16. 数据可视化:

javascript
// 使用D3.js创建数据可视化图表
var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var g = svg.append("g").attr("transform", "translate(40,0)");

var tree = d3.cluster()
    .size([height, width - 160]);

var stratify = d3.stratify()
    .parentId(function(d) { return d.id.substring(0, d.id.lastIndexOf(".")); });

d3.csv("flare.csv", function(error, data) {
  if (error) throw error;

  var root = stratify(data)
      .sort(function(a, b) { return (a.height - b.height) || a.id.localeCompare(b.id); });

  tree(root);

  var link = g.selectAll(".link")
    .data(root.descendants().slice(1))
    .enter().append("path")
      .attr("class", "link")
      .attr("d", function(d) {
        return "M" + d.y + "," + d.x
            + "C" + (d.parent.y + 100) + "," + d.x
            + " " + (d.parent.y + 100) + "," + d.parent.x
            + " " + d.parent.y + "," + d.parent.x;
      });

  var node = g.selectAll(".node")
    .data(root.descendants())
    .enter().append("g")
      .attr("class", function(d) { return "node" + (d.children ? " node--internal" : " node--leaf"); })
      .attr("transform", function(d) { return "translate(" + d.y + "," + d.x + ")"; });

  node.append("circle")
      .attr("r", 2.5);

  node.append("text")
      .attr("dy", 3)
      .attr("x", function(d) { return d.children ? -8 : 8; })
      .style("text-anchor", function(d) { return d.children ? "end" : "start"; })
      .text(function(d) { return d.id.substring(d.id.lastIndexOf(".") + 1); });
});