How to read files in html

Web pages cannot read files directly and need to use front-end frameworks or libraries. Commonly used methods include: XMLHttpRequest object: used for asynchronous data exchange, which can obtain file content by creating objects, opening requests, sending requests, and processing responses. FileReader object: used to read local files. The file content can be obtained by creating objects, adding event handling functions and calling methods. AJAX framework: Provides simpler syntax, such as the $.get() function in jQuery, making reading files more convenient.

How to read files from web pages

HTML itself cannot read files directly. In order to read the file, you need to use a front-end framework or library. The following are the most commonly used methods:

XMLHttpRequest

The XMLHttpRequest object is used for asynchronous data exchange with the server. It allows web pages to read files without refreshing the entire page. The usage steps are as follows:

1. Create an XMLHttpRequest object.
2. Open a request and specify the file path to be read.
3. send request.
4. To process the response, you can use the onload event listener.
5. Use the responseText property to get the file content.

FileReader

The FileReader object is used to read files, usually used to handle local file uploads. The usage steps are as follows:

1. Create a FileReader object.
2. Add an event handling function to the onload event listener to run after the file reading is completed.
3. Call the readAsText() method to read the file content as text.
4. In the onload event handler function, use the result attribute to obtain the file content.

AJAX Framework

AJAX frameworks such as jQuery provide a simplified syntax for reading files. For example, reading a text file using jQuery:

$.get('file.txt', function(data) {
  // 在此处理文件内容
});

Other methods

There are some other ways to read files, but they are less used:

• Iframe: Create a hidden iframe and point it to the file to be read. The file content will be loaded into the iframe and can be obtained using the contentDocument attribute.
• Fetch API: This is the newer method that reads the file using the fetch() function. It returns a Promise that resolves after the read is complete.

Which method to choose

Which method to choose depends on the specific needs:

• XMLHttpRequest Suitable for data exchange with the server.
• FileReader Suitable for reading local files.
• AJAX Framework Provides a simpler syntax, but may be slower.
• Other methods Generally not recommended.

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