Some insights and sharing about js

JavaScript is a scripting language for the Internet!

JavaScript is used by millions of web pages to improve design, validate forms, detect browsers, create cookies, and more.

JavaScript is the most popular scripting language on the Internet.

JavaScript is easy to use! You will love it!

js can now run on

1. Browser side

2. Computer operating system

through the famous node, node is composed of c/ The js running environment written in cpp is probably js that is compiled into c, assembled into machine language. . . Probably

node compilation

js

operating system executable machine language

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Package installation tool

1.npm

2.bower

3.yarn

Now everyone recommends this. . . It is said that it is faster and better

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Build packaging tool (to be honest, I still can’t tell the difference now)

Build tool Task executor

Help compress files? sprite? Obfuscation etc. need manual simplification? Manual labor gulp grunt

Packaging tool Module packaging tool

The modular code is finally assembled and packaged for online use. Webpack browserify and seajs require are packaged on the browser side js on site. Now It is no longer recommended

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js in the page

Traditional introduction method script src

node dynamic introduction

This is a very magical node The tool webpack dynamically assembles your page. For example, if you use the plug-in in node modules, you don't actually use script to introduce it into the page? When you don't understand it yet, you can't use common sense to think about (vue-cli) dev. It is the dynamic assembly build that packages all the dynamic assemblies into one. . .

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es2015==es6 =>true

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jquery attribute self-adding

a.css({'property':'+=value' })

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My current thoughts on vue

First of all, let’s talk about the advantages. It only operates data without operating dom

Let’s talk about the shortcomings. If you want to do a, you need to do b, if you want to do b, if you want to do c, if you want to do a, you need to do b, if you want to do b, if you want to do c, if you want to do a, you need to do b, if you want to do b, if you want to do c, if you want to do a, you need to do b, if you want to do b, if you want to do c, if you want a Do b, do b, do c, do a, do b, do b, do c, do a, do b, do b, do c, do a, do b, do b, do c, do a, do b, do b, do c, do a, do a. Do b, do b, do c, do a, do b, do b, do c, do a, do b, do b, do c, in the end it’s hard to understand. In order to make it more convenient, it becomes more troublesome to add more things

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contenteditable

div simulates textarea rich text editor

<div>
                    <span>#youCantDeleteMe</span><span>
                        <span>Hot or not? Tell it like it is and hashtag!</span>
                        <span> </span>
                    </span>
                </div>

But there are some problems that cannot solve the cursor problem (jumping to the first page). The posting box of Baidu Tieba is simulated using this. If you have time, see how they do it

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Jump according to the device

Three parties can jump and can get the userAgent sent from the browser

1. Operation and maintenance jump

2. Program jump

3. Front-end jump

At the same time, these three parties plus network operators and even routers can maliciously add things to the page using malicious DNS
As a runtime server, node is the same.

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The picture is in the center

1. background-position center

2. ##position absolute

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Multiple lines omitted (modern browsers)

overflow: hidden;text-overflow:ellipsis;display: -webkit-box;-webkit-box-orient:vertical;-webkit-line-clamp:2;

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cdn page true dynamic content

The page is cached by the cdn server After that, the cache needs to be refreshed to really change, then the content that really needs to be changed needs to be obtained by js (such as the currently logged in user information, etc.)

js Regularly finds all matching matches

var regEx=/js_quantity[a-z]+/g;regEx.exec('js_quantityabc js_quantityminus minus disabled');regEx.exec('js_quantityabc js_quantityminus minus disabled');regEx.exec('js_quantityabc js_quantityminus minus disabled')
[0];regEx.exec('js_quantityabc js_quantityminus minus disabled').index;

Continuously execute exec

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async/await

demo(Script snippet #1)

//测试 async async async await//先来的 返回一个promise 完成时调用resolvevar sleep=function(){ return new Promise(function(resolve,reject){
     setTimeout(function(){         console.log('Asettimeout has been executed, promiss has been resolved');
         resolve(['sleep1','sleep2']);
     },3000);
 });
};//后到的 async（异步）修饰function await修饰执行先来的var start=async function(){ let sleepreturnarray=await sleep(); console.log('%ceven though i do not have a time out, i still will be executed after 3 sec, after the promiss resolveed'+sleepreturnarray[1],'color:red;');
};
start();

async means that this is an async function, and await can only be used in this inside the function.

await means waiting for the promise to return the result before continuing execution.

await should be followed by a promise object (of course, other return values ​​​​do not matter, they will just be executed immediately, but that would be meaningless...)

A lot said, Currently this is the ultimate solution to asynchronous callback hell, of course combined with babel. Note that at present, Ultimate

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vue component communication

Even if you don’t like it, you have to use it if you are assigned to use it. . .

The scopes between components are independent, and data often needs to be passed between components.

A is the parent component, and there are subcomponents B and C below.
A’s data can be passed to B and C through props.
A can call events of B and C through $broadcast to operate the data of B and C.
B and C can call A's events through $dispatch to manipulate A's data.
When B needs to operate C's data, it will be more troublesome. It needs to $dispatch to A first, and then $broadcast to C.

It’s okay if the project is relatively small. The larger the project, the more and more frequent the components involved will communicate. At this time, management will be very tiring and error-prone. This is what Vuex is all about. It can place data in a separate layer and provide methods for external manipulation of internal data. It’s a bit vulgar, so let’s understand it.

=== === ===Update: Vue 2 has been released, $dispatch and $broadcast have been removed, and the communication event ping-pong will no longer occur.

We need a Vue instance to act as a communication medium. The official Vue documentation calls it event bus. export default new Vue(); When we need event communication between components, we only need to use $emit and $on on this event bus.

import Bus from './bus.js';

export default Vue.extend({
  template: `
  <div>{{msg}}</div>
  `,

  data: () => ({
    msg: 'Hello World!'
  }),

  created() {
    Bus.$on('setMsg', content => {
      this.msg = content;
    });
  }
});

import Bus from './bus.js';

export default Vue.extend({
  template: `
  <div>Say Hi</div>
  `,

  methods: {
    sendEvent() {
      Bus.$emit('setMsg', 'Hi Vue!');
    }
  }
});

Event bus is a practice that you can also use in Vue 1.x.

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Large is centered in a small container

法一

Large: position absolute; left 50%; margin-left -[half of the width of the large ]; top...Omit the same as left

Small: position relative;

法二

设置为背景图 且background-position center

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文本框和按钮同高对齐(less)

form{			font-size: 0;position: relative;			.formitem{				height: 30px;line-height: 30px;				font-size: 14px;vertical-align: middle;
			}			input[type=text]{				.formitem();				border: 1px solid #000;				padding: 0 5px 0 35px;				width: 235-40px;
			}			button{				.formitem();				color: #fff;background-color: #000;				width: 135px;height: 32px;line-height: 32px;
			}			&:before{				content: '';display: inline-block;position: absolute;				left: 38px;				top: 1px;				.sprite(@youjiandingyue_07);
			}
		}

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正则替换 保留原始内容

http://([A-Za-z0-9.-]+).sammydress.com
https://$1.sammydress.com

$1 是代表([A-Za-z0-9.-]+)匹配到的模糊内容
$1-$n分别代表第1个和第n个括号内匹配到的内容。

var regEx=/([A-Za-z0-9.-]+)abc/;'sdjlfjslfabc'.replace(regEx,'$1def')

结果是"sdjlfjslfdef"

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关于vue一点新的体会

专注于操作数据，数据和视图分离，通过操作数据的方式操作视图，mvvm
而不是$().html()等等这种形式

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webstorm 保存不会触发webpack watch

原来是这样啊啊啊啊啊啊

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text align justify

text-align:justify 属性是全兼容的，使用它实现两端对齐，需要注意在模块之间添加[空格/换行符/制表符]才能起作用，同样，实现文本对齐也是需要在字与字之间添加[空格/换行符/制表符]才能起作用

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vue validator

中文文档

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关于postcss中用于不转换rem的注释/*no*//*px*/在webpack build中不生效的解决办法

sass loader会把注释去掉 导致用于告诉postcss不用转换rem的注释也去掉 导致边线px变成小数rem 显示不出来的bug
sass?outputStyle=expanded 展开 带注释的？

module: {loaders: [
            {test: /\.scss$/,//感謝谷歌loader: 'style!css!postcss-loader!sass?outputStyle=expanded',// include: APP_PATH},
        ]
    },

webpack 可以接受形如!sass?outputStyle=expanded&sourceMap=true&sourceMapContents=true&includePaths[]=./node_modules 的配置参数后的loader

 

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