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What should I do if the react framework meets Baidu Maps?

零下一度

Jun 26, 2017 pm 01:38 PM

react map frame Baidu

The usage instructions of Baidu Map official document say this: Introduce , then you can use the BMap object introduced in the script to call various APIs

The problem I encountered:

After I introduced the above script in the entry file - index.html, when I accessed BMap in another JS file, an error was reported, prompting that BMap is not defined,

My ideas for solving the problem:

1. Go to github Find out if there is an open source SDK (if there is, install the dependency package through npm install, and then I can introduce BMap through require or import) ——Failed, there is no open source dependency package at all

2. Directly introduce the http address through require or import, such as require('http..../*The address of the above script*/')—— Failure, require or import can only directly introduce local resource files, and cannot directly introduce external

3. Bind BMap to the Window object to achieve cross-file access - success! (It can be implemented but not recommended, implemented for the sake of implementation)

4. Implement require access through the externals attribute in the webpack output object ——Success ! (Recommended practice)

Reproduce the problem:

My directory:

##My index.html looks like this:

1	`/剩下的部分自己想象/<script type="text/javascript"` `src="http://api.map.baidu.com/api?v=2.0&ak=我的的秘钥"></script>/剩下的部分自己想象/`

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My test/index.js looks like this:

import React from 'react'
 class Test extends React.Component{
componentDidMount () {   var map = new BMap.Map("allmap")
}
render () {return (<div id=&#39;allmap&#39;></div>)   }
}

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However, an error was reported when rendering Test:

A fact In front of you:

When building an application in a modular manner, you cannot directly access the variables in the entry file in the JS module, So How do we import the variables in the entry HTML file into a JS file?

#Or in this example, how can we obtain the BMap object in the script introduced in HTML in test/index.js?

Maybe many students will think: Just use export/import! But exporting variables directly in HTML files is obviously not a reasonable approach

Method 1: Save BMap with Window object Variables, realizing variable transfer between HTML files and JS files：

在引入百度地图的脚本下再加入这一段脚本：

1 2	`<script type="text/javascript"` `src="http://api.map.baidu.com/api?v=2.0&ak=eBGR7XzaPhB5UbYARl3E7ksdkMdgrCw7"></script>` `<script> window.BMap = BMap</script>`

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没错，就是把BMap对象保存到全局可访问的window对象中

当要使用BMap的时候这样用：

1	`BMap = window.BMap map = BMap.Map("allmap");`

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例子如下：

import React from 'react'import ReactDOM from 'react-dom'class BaiduMap extends React.Component {
  
componentDidMount () {  var BMap = window.BMap  var map = new BMap.Map("allmap"); // 创建Map实例
  map.centerAndZoom(new BMap.Point(116.404, 39.915), 11); // 初始化地图,设    置中心点坐标和地图级别
  map.addControl(new BMap.MapTypeControl()); //添加地图类型控件
  map.setCurrentCity("北京"); // 设置地图显示的城市 此项是必须设置的
  map.enableScrollWheelZoom(true); //开启鼠标滚轮缩放}
  
render () {  return (<div>
    <div
      id=&#39;allmap&#39;  style={{
        width:&#39;100vw&#39;,
        height:&#39;100vh&#39;  }} />
</div>    )
  }
}
ReactDOM.render(<BaiduMap />,
document.getElementById('root')
)

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demo:

方法二.通过webpack的externals加载BMap使它可以通过require或import引入

在webpack.config.js中

module.exports = {/*此处省略了entry，output,modules等配置*/
  externals:{    'BMap':'BMap'
  },
}

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在使用到BMap的时候，这样引入：

1	`import BMap from` `'BMap'var` `map =` `new` `BMap.Map("allmap");` `// 创建Map实例//通过map调用API`

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例子：

import React from 'react'import ReactDOM from 'react-dom'import BMap from 'BMap'class BaiduMap extends React.Component {
  
componentDidMount () {  var map = new BMap.Map("allmap"); // 创建Map实例
  map.centerAndZoom(new BMap.Point(116.404, 39.915), 11); // 初始化地图,设置中心点坐标和地图级别
  map.addControl(new BMap.MapTypeControl()); //添加地图类型控件
  map.setCurrentCity("北京"); // 设置地图显示的城市 此项是必须设置的
  map.enableScrollWheelZoom(true); //开启鼠标滚轮缩放}
  
render () {  return (<div>
      <div
        id=&#39;allmap&#39;style={{
          width:&#39;100vw&#39;,
          height:&#39;100vh&#39; }} />
    </div>       )
       }
}
ReactDOM.render(  <BaiduMap />,
  document.getElementById('root')
)

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webpack的externals的具体作用我概括为两点：

1.写入externals中的依赖是不会被打包进最后的bundle里面的

2.虽然它不会被打包，但在程序运行的时候你仍然能通过模块化的方式去引入这些依赖，如commonJS,AMD,ES6的import等

（原文：Prevent bundling of certain imported packages and instead retrieve these external dependencies at runtime.）

demo同上：

百度地图新手（尤其是用react的）容易犯的错误及其解决方式：

1.忘记写

这个元素(id不一定要是allmap,只要和 new BMap.map（参数）里的字符串参数相同便可)

然后控制台就会报：TypeError: Cannot read property 'gc' of undefined的错误

解决方法：记得写

2.你写入了

，但还是报了TypeError: Cannot read property 'gc' of undefined的错误，你可能犯了一个原生JS码农不太可能会犯但是react码农可能会犯的错误：你在

渲染前就执行了 var map = new BMap.Map("allmap");这一行代码

例如：

render () {   var map = new BMap.Map("allmap"); // 创建Map实例
   return (<div id=&#39;allmap&#39; />) )
}

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解决办法：在渲染

后才执行var map = new BMap.Map("allmap"); 例如将初始化map的代码放入组件类的

componentDidMount （）钩子函数中（这个函数将在组件被初次渲染完毕后调用）

例如：

class BaiduMap extends React.Component {
componentDidMount () {    var map = new BMap.Map("allmap"); // 创建Map实例}
render () {    return <div id=&#39;allmap&#39; /> )
}

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3.你写入了

，控制台也没有报错，但是你就是看！不！到！地！图！

这多半是你没有给

加上宽高，百度地图的API是不会给你的div加宽高的，所以height默认是0就是0

解决方法：给目标地图div加上宽高（严格地说是高，宽默认为width:auto）

1 2	`render () {return` `<div id='allmap' style={{width:'100%',height:'100px'}} />` `}`

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为此，我写了一封反馈的信件给百度地图的工作者们，目前在等待回应中（希望能有所回应吧）

以下为详细内容：

亲爱的百度地图开发者您好，作为一名react框架开发者，我在入门百度地图API时遇到困难——我不知道如何在模块化JS中使用BMap的API（问题现已解决）。因为你们只提供了原生JS下的入门指导，而没有任何关于模块化JS编程下的指导内容。这对于一些框架新手来说确实有些难以下手

我遇到的问题是：在引入携带AK的script的前提下，在一个JS模块文件（不是入口文件）中使用BMap报错："error! BMap is not defined!"

我的解决法是通过在Webpack输出对象中的externals属性中加入BMap:"BMap"，然后通过在对后在对应的JS页面中通过Window.BMap取得。

希望你们能够提供更为详细的操作指导，例如webpack下BMap的用法。这将让你们的产品变得更好。

以上 —— 某个爱好javaScript的大二学生

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