What local file formats does javascript have?

JavaScript is a programming language that can run in the client browser. It can interact with local storage, read and write various local file formats. In this article, we will explore how JavaScript handles the following local file formats.

1. Text file

A text file is an ordinary ASCII text file that consists of a series of lines with a newline character at the end of each line. JavaScript can use the XMLHttpRequest object and AJAX to read a text file from the server and manipulate and display the file on the client.

An example is to read a text file using the following code:

var xmlhttp = new XMLHttpRequest();

xmlhttp.onreadystatechange = function() {
  if (this.readyState == 4 && this.status == 200) {
    var myText = this.responseText; //保存文本文件内容到变量
    //在页面上展示文本文件内容
    document.getElementById("myText").innerHTML = myText;
  }
};

xmlhttp.open("GET", "textfile.txt", true);
xmlhttp.send();

2. JSON file

JSON file is a lightweight format that Can be used to store structured data. JavaScript has built-in JSON objects, which can easily parse JSON files into JavaScript objects and use the JavaScript language to process the properties and methods of the object.

For example, you can use the following code to read a JSON file:

var xmlhttp = new XMLHttpRequest();

xmlhttp.onreadystatechange = function() {
  if (this.readyState == 4 && this.status == 200) {
    var myObj = JSON.parse(this.responseText); //将JSON文件解析为JavaScript对象
    //在页面上展示JavaScript对象的某些属性
    document.getElementById("name").innerHTML = myObj.name;
    document.getElementById("age").innerHTML = myObj.age;
  }
};

xmlhttp.open("GET", "jsonfile.json", true);
xmlhttp.send();

3. XML file

XML file is a markup language that consists of tags and Composed of attributes, used to store structured data. JavaScript can read an XML file from the server using the XMLHttpRequest object and AJAX, and manipulate the file using JavaScript DOM methods.

For example, the following code can be used to read an XML file:

var xmlhttp = new XMLHttpRequest();

xmlhttp.onreadystatechange = function() {
  if (this.readyState == 4 && this.status == 200) {
    var xmlDoc = this.responseXML; //将XML文件解析为JavaScript DOM对象
    //在页面上展示XML文件的某些元素
    document.getElementById("author").innerHTML = xmlDoc.getElementsByTagName("author")[0].childNodes[0].nodeValue;
    document.getElementById("title").innerHTML = xmlDoc.getElementsByTagName("title")[0].childNodes[0].nodeValue;
  }
};

xmlhttp.open("GET", "xmlfile.xml", true);
xmlhttp.send();

4. Image file

An image file is a media file that can be read using JavaScript Display in browser. JavaScript can use the Image object and HTML DOM to operate image files.

For example, you can use the following code to display image files:

var img = new Image();
img.src = "imagefile.jpg";
document.body.appendChild(img); //在HTML页面中展示图片

Summary

By using JavaScript, we can easily handle various local file formats, including text files, JSON files, XML files and image files. These local file formats have many applications in network programming and Web development. Mastering JavaScript file processing skills will help improve our programming and development capabilities.

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