What should I do if the interface cannot be called when uniapp is published as h5?

Recently, many developers have encountered a problem when building applications using uniapp: after publishing the application as H5, the API interface cannot be called. This problem may seem difficult to solve, but in fact, it only takes a few tweaks to fix it.

First, let us understand what uniapp is. uniapp is a cross-platform development framework based on Vue.js, supporting multi-end publishing, including H5, iOS, Android and other platforms. The emergence of uniapp allows developers to use Vue.js to develop native applications, and only need to write code once to publish to multiple platforms at the same time.

However, when we publish the uniapp application as H5, we may find that the API interface cannot be called. This is due to cross-domain issues. When we access a page in a browser, if the page needs to call an API interface from a different domain, the browser will block this operation to prevent cross-site scripting attacks.

So, how to solve this problem?

A common solution is to set up CORS (Cross-Origin Resource Sharing) on ​​the server side. CORS is a mechanism that allows applications under the same domain name to access resources under another domain name. Using CORS requires setting response header information on the server side to allow cross-domain access by the client. However, for many developers, this is not very easy to implement as it may require changing the server configuration or finding a service provider that supports CORS.

Another solution is to use JSONP. With the popularity of H5 applications, JSONP has become more and more popular. JSONP is a cross-domain request method that allows a script from another domain to be loaded on the page and parameters are passed to the server when loading. How JSONP works is that the client references a JavaScript file on the page, which triggers a callback function and passes it to the server as a parameter. After the server receives the request, it will encapsulate the data in the callback function and return it, and the client can obtain the data through the callback function.

Using JSONP in uniapp is very simple. You can use the uni.request method to make cross-domain requests:

uni.request({
  url: 'http://example.com/api/data',
  method: 'GET',
  dataType: 'jsonp',
  success: function (res) {
    console.log(res.data)
  }
})

In the above example, we set the dataType to jsonp to tell the server that we need to use JSONP to handle the request. After the server receives the request, it will return a response in JSONP format. On the client side, we can use a callback function to handle the JSONP response:

function handleResponse(data) {
  console.log(data)
}

<script src="http://example.com/api/data?callback=handleResponse"></script>

In this example, we add a script tag to the page and set the src attribute to the request URL, and add callback parameters. When the browser loads this URL, the server will encapsulate the data into the callback function and return it in the form of JavaScript code. The callback function on the page will be called and the response data will be obtained.

In short, if the application built using uniapp cannot call the API interface after being published as H5, you can consider using JSONP to solve the cross-domain problem. If CORS is easier to implement for you, you can also try setting up CORS on the server side. No matter which method is used, your application can run normally on the H5 platform.

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