How to use JavaScript to modify and save data

In front-end development, we often need to use JavaScript to achieve some interactive effects and logical processing. Among them, modifying and saving data is also one of the common requirements. This article will introduce how to use JavaScript to modify and save data.

1. Overview

In common websites and applications, users usually need to change content or manipulate data. These changed content or data need to be saved to the back-end server or local hard drive. Therefore, we need to use JavaScript to call the corresponding API to implement the data saving function.

2. Data types

Before realizing data saving, we need to know how different types of data should be processed. Normally, we can divide data into the following two categories:

1. Form data: Form data is usually form data filled in by users, such as text boxes, drop-down boxes, radio button boxes, etc. This data can be obtained through JavaScript's document.forms property, then processed in JSON format, and then sent to the backend server through AJAX for saving.
2. Local data types: Local data types include Cookie, Web Storage, IndexedDB, etc. This data can be used to save user login information, application settings, business data, etc.

3. Form data storage

Form data is one of the most common types. We can use JavaScript and AJAX to send form data to the back-end server. The following is an example:

document.getElementById("saveButton").addEventListener("click", function(){
  var form = document.forms["myForm"];
  var formData = new FormData(form);

  var xhr = new XMLHttpRequest();
  xhr.open("POST", "/saveData.php");
  xhr.send(formData);

  xhr.onreadystatechange = function() {
    if(xhr.readyState === 4 && xhr.status === 200) {
      console.log(xhr.responseText);
    }
  }
});

In this example, we use the addEventListener method to add a click event. This event sends the form data to the /saveData.php file through the POST method of the XMLHttpRequest object. When the server returns a response, we print the text it returned on the console.

4. Web Storage Save

Web Storage is a type of browser local storage API. It can be accessed through localStorage and sessionStorage objects. The following is an example:

// 存储数据
localStorage.setItem("username", "Jack");
localStorage.setItem("age", "25");

// 读取数据
var username = localStorage.getItem("username");
var age = localStorage.getItem("age");

// 删除数据
localStorage.removeItem("username");
localStorage.clear(); // 删除所有数据

The above code demonstrates how to use localStorage to store and read data. This data will remain in the browser until manually cleared or until the storage limit is reached.

5. Summary

This article introduces the method of using JavaScript to modify and save data, including form data saving and Web Storage storage. These technologies can greatly improve user experience and improve application performance and efficiency. Of course, in practical applications, we need to choose the most appropriate data type and storage method according to specific scenarios to meet user needs.

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