添加jQuery以反应入门工具包

Question

我是Java语言世界的新手，并开始创建一个简单的React项目，该项目是使用React Starter Kit启动的，并添加了我的第一个模块，其中一个简单的上传文件是：

上传文件。

import React, { Component, PropTypes } from 'react';
import FormData from 'form-data';
import $ from 'jquery';

class UploadPanel extends Component {
  state = {
    file:'',
  };
  uploadSelectedFile() {

    // Add the uploaded image content to the form data collection
    var data = new FormData();
    data.append("image", this.state.file);
    data.append("temp", 'temp');
    $.ajax({
      method: "POST",
      url: "rest/dicom/upload",
      xhr: function () {  // Custom XMLHttpRequest
        var myXhr = $.ajaxSettings.xhr();
        return myXhr;
      },
      cache: false,
      data: data,
      contentType: false,
      processData: false,
      success: function (data) {
        alert('file sent');
        console.log(data);
      },
      error: function (data) {
        alert('error');
        console.log(data);
      }
    });
  }
  handleFileChange(e){
    let file = e.target.files;
    if(file.length>0)
      this.setState({file: file});
    else
      this.setState({file: ''});
  }

  render() {
    //return <p> hi this is a test </p>
    //var createItem = function (item) {
    //  return <li key={item.id}>{item.text}</li>;
    //};

    return <form onSubmit={this.uploadSelectedFile()}>
      <input type="file" name="image" id="image" value={this.state.file} onChange={this.handleFileChange}/>
      <input type="submit" value="ارسال"  disabled={this.state.file!=''}/>
    </form>;
  }
}


export default UploadPanel;

但是当我打开页面时，（在服务器中）编译出现以下错误：

TypeError: _jquery2.default.ajax is not a function
at UploadPanel.uploadSelectedFile (D:\Projects\Behyaar\BOIS\ReactDashboardClient\build\webpack:\src\components\bois\UploadDicom\UploadPanel.js:24:7)
at UploadPanel.render (D:\Projects\Behyaar\BOIS\ReactDashboardClient\build\webpack:\src\components\bois\UploadDicom\UploadPanel.js:59:33)
at ReactCompositeComponentMixin._renderValidatedComponentWithoutOwnerOrContext (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactCompositeComponent.js:587:34)
at ReactCompositeComponentMixin._renderValidatedComponent (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactCompositeComponent.js:607:32)
at wrapper [as _renderValidatedComponent] (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactPerf.js:66:21)
at ReactCompositeComponentMixin.mountComponent (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactCompositeComponent.js:220:30)
at wrapper [as mountComponent] (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactPerf.js:66:21)
at Object.ReactReconciler.mountComponent (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactReconciler.js:37:35)
at ReactDOMComponent.ReactMultiChild.Mixin.mountChildren (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactMultiChild.js:241:44)
at ReactDOMComponent.Mixin._createContentMarkup (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactDOMComponent.js:591:32)
at ReactDOMComponent.Mixin.mountComponent (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactDOMComponent.js:479:29)
at Object.ReactReconciler.mountComponent (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactReconciler.js:37:35)
at ReactCompositeComponentMixin.mountComponent (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactCompositeComponent.js:225:34)
at wrapper [as mountComponent] (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactPerf.js:66:21)
at Object.ReactReconciler.mountComponent (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactReconciler.js:37:35)
at ReactDOMComponent.ReactMultiChild.Mixin.mountChildren (D:\Projects\Behyaar\BOIS\ReactDashboardClient\node_modules\react\lib\ReactMultiChild.js:241:44)

有人可以帮忙吗？ 为什么要在服务器中运行客户端代码？

Answer 1

在您的render函数中，您在语法上犯了一个小错误（我认为这是在React中吸引所有人的地方，尤其是当它们来自其他框架时）。 看这行：

return <form onSubmit={this.uploadSelectedFile()}> ... </form>

函数名称末尾带有方括号-换句话说，每次render函数运行时，包括在服务器上，您都在调用该函数！

演示的最佳方法是将JSX转换为将实际运行的JavaScript：

return React.createElement("form", { onSubmit: this.uploadSelectedFile() });

您正在将onSubmit属性设置为this.uploadSelectedFile的返回值 ，而不是函数本身。

您需要修复两件事-首先，从前面提到的语句的末尾删除括号。 第二件事不太明显-在使用ES6类时， 需要明确地将函数绑定到正确的this值 ：

class UploadPanel extends Component {
    ...
    constructor() {
        super();
        this.uploadSelectedFile = this.uploadSelectedFile.bind(this);
        this.handleFileChange = this.handleFileChange.bind(this);
    }
    ...
}

如果您使用的是stage-0 Babel预设，还可以通过箭头功能使用更优雅的方式进行此操作。

希望这可以为您清除一切！