How to use JSONP for cross-domain requests in Vue projects

How to use JSONP for cross-domain requests in the Vue project

Introduction:
In the Vue project, sometimes you will encounter the need to obtain data from different domain names For example, to obtain data by calling a third-party API, under normal circumstances, direct cross-domain requests are prohibited due to the browser's same-origin policy. But in some cases, we can use JSONP technology to implement cross-domain requests. This article will introduce how to use JSONP to make cross-domain requests in the Vue project and give specific code examples.

1. JSONP working principle:
JSONP (JSON with Padding) is a technology that implements cross-domain requests by dynamically creating <script></script> tags. It takes advantage of the fact that the <script></script> tag can be accessed across domains. The specific implementation steps are as follows:

1. The client creates a URL with a callback function and assigns the URL to the src of the <script></script> tag. Attributes.
2. After the server receives this request, it parses the callback function name in the URL, wraps the data in the callback function, and returns it.
3. After the client receives the script returned by the server, it will immediately execute the script, thereby triggering the callback function and processing the returned data.

2. Use JSONP to make cross-domain requests in the Vue project:
Below we will explain the specific steps on how to use JSONP to make cross-domain requests in the Vue project.

1. Install jsonp library:
   Using JSONP in a Vue project requires installing the jsonp library, which can be installed using npm. Execute the following command in the terminal to install:

   npm install jsonp

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   After the installation is completed, we can introduce the jsonp library into the Vue project.

2. Create JSONP request:
   In a Vue project, we usually create a JSONP request in a method of a component. The following is an example of obtaining weather data. The specific code is as follows:

   import jsonp from 'jsonp';
   
   export default {
     methods: {
    getWeather() {
      const url = 'http://api.weather.com/weatherData?callback=weatherCallback';
      jsonp(url, (err, data) => {
        if (err) {
          console.log(err);
        } else {
          this.weatherData = data; // 处理返回的数据
        }
      });
    }
     }
   }

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   The above code first introduces the jsonp library and creates a JSONP request in the getWeather method. The request URL contains a callback parameter whose value is the defined callback function name weatherCallback. The JSONP library will pass the data returned by the server into the callback function, and then we can process the returned data in the callback function.

3. Call the method in the template:
   In the Vue project, we can bind the getWeather method to the click event of a button. The specific code is as follows:

   <template>
     <div>
    <button @click="getWeather">获取天气</button>
     </div>
   </template>

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4. Processing the returned data:
   In the getWeather method, after obtaining the data returned by the server through JSONP, we can process the data, such as displaying the data on the page. The specific code is as follows:

   <template>
     <div>
    <button @click="getWeather">获取天气</button>
    <div v-if="weatherData">
      <p>城市：{{ weatherData.city }}</p>
      <p>温度：{{ weatherData.temperature }}</p>
    </div>
     </div>
   </template>

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Summary:
This article introduces the steps of how to use JSONP to make cross-domain requests in the Vue project. First, we need to install the jsonp library, then create a JSONP request in a certain method and process the data in the returned callback function. Finally, call this method in the template to display the returned data on the page. Using JSONP can solve some cross-domain request problems, but you need to pay attention to issues such as security and compatibility, and make appropriate choices based on specific needs.

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