JavaScript把局部变量变成全局变量

流楚丶格念 2021-07-20 03:52:37
javascript


首先我们要知道函数的自调用

函数的自调用——自调用函数

一次性的函数——声明的同时,直接调用了
例如:

(function () {
console.log("函数");
})();

  • 1.
  • 2.
  • 3.
  • 4.

我们会看到浏览器直接打印 函数 两个字

页面加载后.这个自调用函数的代码就执行完了

使用形式

(function (形参) {
})(实参);

  • 1.
  • 2.
  • 3.

注意

  • 自调用构造函数的方式,分号一定要加上

那么如何把局部变量变成全局变量?

把局部变量给window就可以了


(function (win) {
var num=10;//局部变量
//js是一门动态类型的语言,对象没有属性,点了就有了
win.num=num;
})(window);
console.log(num);

  • 1.
  • 2.
  • 3.
  • 4.
  • 5.
  • 6.
  • 7.

页面打印出num了
在这里插入图片描述

应用案例1——将随机数对象赋给window

在这里插入图片描述

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>title</title>
<script>
//通过自调用函数产生一个随机数对象,在自调用函数外面,调用该随机数对象方法产生随机数
(function (window) {
//产生随机数的构造函数
function Random() {
}
//在原型对象中添加方法
Random.prototype.getRandom = function (min,max) {
return Math.floor(Math.random()*(max-min)+min);
};
//把Random对象暴露给顶级对象window--->外部可以直接使用这个对象
window.Random=Random;
})(window);
//实例化随机数对象
var rm=new Random();
//调用方法产生随机数
console.log(rm.getRandom(0,5));
//全局变量
</script>
</head>
<body>
</body>
</html>

  • 1.
  • 2.
  • 3.
  • 4.
  • 5.
  • 6.
  • 7.
  • 8.
  • 9.
  • 10.
  • 11.
  • 12.
  • 13.
  • 14.
  • 15.
  • 16.
  • 17.
  • 18.
  • 19.
  • 20.
  • 21.
  • 22.
  • 23.
  • 24.
  • 25.
  • 26.
  • 27.
  • 28.
  • 29.
  • 30.
  • 31.
  • 32.
  • 33.
  • 34.

应用案例2——产生随机位置小方块

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta >
<title>title</title>
<style>
.map{
width: 800px;
height: 600px;
background-color: #CCC;
position: relative;
}
</style>
</head>
<body>
<div class="map"></div>
<script src="common.js"></script>
<script>
//产生随机数对象的
(function (window) {
function Random() {
}
Random.prototype.getRandom=function (min,max) {
return Math.floor(Math.random()*(max-min)+min);
};
//把局部对象暴露给window顶级对象,就成了全局的对象
window.Random=new Random();
})(window);//自调用构造函数的方式,分号一定要加上
//产生小方块对象
(function (window) {
//console.log(Random.getRandom(0,5));
//选择器的方式来获取元素对象
var map=document.querySelector(".map");
//食物的构造函数
function Food(width,height,color) {
this.width=width||20;//默认的小方块的宽
this.height=height||20;//默认的小方块的高
//横坐标,纵坐标
this.x=0;//横坐标随机产生的
this.y=0;//纵坐标随机产生的
this.color=color;//小方块的背景颜色
this.element=document.createElement("div");//小方块的元素
}
//初始化小方块的显示的效果及位置---显示地图上
Food.prototype.init=function (map) {
//设置小方块的样式
var div=this.element;
div.style.position="absolute";//脱离文档流
div.style.width=this.width+"px";
div.style.height=this.height+"px";
div.style.backgroundColor=this.color;
//把小方块加到map地图中
map.appendChild(div);
this.render(map);
};
//产生随机位置
Food.prototype.render=function (map) {
//随机产生横纵坐标
var x=Random.getRandom(0,map.offsetWidth/this.width)*this.width;
var y=Random.getRandom(0,map.offsetHeight/this.height)*this.height;
this.x=x;
this.y=y;
var div=this.element;
div.style.left=this.x+"px";
div.style.top=this.y+"px";
};
//实例化对象
var fd=new Food(20,20,"green");
fd.init(map);
console.log(fd.x+"===="+fd.y);
})(window);
// function refresh(){
// window.location.reload();
// }
// setTimeout(refresh(), 1000);
</script>
</body>
</html>

  • 1.
  • 2.
  • 3.
  • 4.
  • 5.
  • 6.
  • 7.
  • 8.
  • 9.
  • 10.
  • 11.
  • 12.
  • 13.
  • 14.
  • 15.
  • 16.
  • 17.
  • 18.
  • 19.
  • 20.
  • 21.
  • 22.
  • 23.
  • 24.
  • 25.
  • 26.
  • 27.
  • 28.
  • 29.
  • 30.
  • 31.
  • 32.
  • 33.
  • 34.
  • 35.
  • 36.
  • 37.
  • 38.
  • 39.
  • 40.
  • 41.
  • 42.
  • 43.
  • 44.
  • 45.
  • 46.
  • 47.
  • 48.
  • 49.
  • 50.
  • 51.
  • 52.
  • 53.
  • 54.
  • 55.
  • 56.
  • 57.
  • 58.
  • 59.
  • 60.
  • 61.
  • 62.
  • 63.
  • 64.
  • 65.
  • 66.
  • 67.
  • 68.
  • 69.
  • 70.
  • 71.
  • 72.
  • 73.
  • 74.
  • 75.
  • 76.
  • 77.
  • 78.
  • 79.
  • 80.
  • 81.
  • 82.
  • 83.
  • 84.
  • 85.
  • 86.
  • 87.
版权声明
本文为[流楚丶格念]所创,转载请带上原文链接,感谢
https://blog.51cto.com/u_15265965/2891976

  1. HTML + CSS + JavaScript to achieve cool Fireworks (cloud like particle text 3D opening)
  2. HTML + CSS + JavaScript realizes 520 advertising love tree (including music), which is necessary for programmers to express themselves
  3. Solve the problem of Web front-end deployment server (it can be deployed online without a server)
  4. HTML + CSS + JS make wedding countdown web page template (520 / Tanabata Valentine's Day / programmer advertisement)
  5. What else can driverless minibus do besides "Park connection"?
  6. Cloud native leads the era of all cloud development
  7. NRM mirror source management tool
  8. Bring it to you, flex Jiugong
  9. Lolstyle UI component development practice (II) -- button group component
  10. Deconstruction assignment in ES6
  11. Luo 2 peerless Tang clan was officially launched. The official gave a key point, and the broadcast time was implied
  12. 20初识前端HTML(1)
  13. 当新零售遇上 Serverless
  14. 20 initial knowledge of front-end HTML (1)
  15. When new retail meets serverless
  16. [golang] - go into go language lesson 5 type conversion
  17. [golang] - go into go language lesson 6 conditional expression
  18. HTML5(八)——SVG 之 path 详解
  19. HTML5 (8) -- detailed explanation of SVG path
  20. 需要开通VIP以后页面内容才能复制怎么办?控制台禁用javascript即可
  21. Web前端|CSS入门教程(超详细的CSS使用讲解,适合前端初学者)
  22. 实践积累 —— 用Vue3简单写一个单行横向滚动组件
  23. Serverless 全能选手,再下一城
  24. What if you need to open a VIP to copy the page content? Just disable JavaScript on the console
  25. Web front end | CSS introductory tutorial (super detailed CSS explanation, suitable for front-end beginners)
  26. Practice accumulation - write a single line horizontal scroll component simply with vue3
  27. Dili Reba is thin again. She looks elegant and high in a strapless hollow skirt, and her "palm waist" is beautiful to a new height
  28. Serverless all-round player, next city
  29. The difference between MySQL semi synchronous replication and lossless semi synchronous replication
  30. Vue表单设计器的终极解决方案
  31. The ultimate solution for Vue form designer
  32. Nginx从理论到实践超详细笔记
  33. Yu Shuxin's red backless swimsuit is split to the waist and tail, with a concave convex figure and excessive color matching, and his face is white to dazzling
  34. Nginx ultra detailed notes from theory to practice
  35. 【动画消消乐|CSS】086.炫酷水波浪Loading过渡动画
  36. typecho全站启用https
  37. CCTV has another popular employee. The off-site interpretation is very professional, and the appearance ability is no less than that of Wang Bingbing
  38. [animation Xiaole | CSS] 086. Cool water wave loading transition animation
  39. Enable HTTPS in Typecho
  40. 50天用JavaScript完成50个web项目,我学到了什么?
  41. 根据JavaScript中原生的XMLHttpRequest实现jQuery的Ajax
  42. What have I learned from completing 50 web projects with JavaScript in 50 days?
  43. "My neighbor doesn't grow up" has hit the whole network. There are countless horse music circles, and actor Zhou Xiaochuan has successfully made a circle
  44. 根据JavaScript中原生的XMLHttpRequest实现jQuery的Ajax
  45. Implement the Ajax of jQuery according to the native XMLHttpRequest in JavaScript
  46. Implement the Ajax of jQuery according to the native XMLHttpRequest in JavaScript
  47. 30 + women still wear less T-shirts and jeans. If they wear them like stars, they will lose weight
  48. 数栈技术分享前端篇:TS,看你哪里逃~
  49. Several stack technology sharing front end: TS, see where you escape~
  50. 舍弃Kong和Nginx,Apache APISIX 在趣链科技 BaaS 平台的落地实践
  51. Abandon the landing practice of Kong and nginx, Apache apisik on the baas platform of fun chain technology
  52. 浪迹天涯king教你用elementui做复杂的表格,去处理报表数据(合并表头,合并表体行和列)
  53. 前端HTML两万字图文大总结,快来看看你会多少!【️熬夜整理&建议收藏️】
  54. Wandering around the world king teaches you to use elementui to make complex tables and process report data (merge header, merge table body rows and columns)
  55. 路由刷新数据丢失 - vuex数据读取的问题
  56. Front end HTML 20000 word graphic summary, come and see how much you can【 Stay up late to sort out & suggestions]
  57. Route refresh data loss - vuex data reading problem
  58. Systemctl系统启动Nginx服务脚本
  59. Systemctl system startup nginx service script
  60. sleepless