javascript text editor implementation code

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JavaScript text editor implementation code

JavaScript is a scripting language widely used in Web development. The biggest advantage is that you can dynamically change a certain part of the page without reloading the entire page. The text editor is one of the most commonly used tools by programmers. JavaScript can help us write an easy-to-use editor that can implement text editing functions. This article will introduce the code to implement a text editor through JavaScript.

1. Implement the text box

First, we need to insert a text box in the HTML code and set an ID for it for subsequent JavaScript calls.

<textarea id="editor"></textarea>

2. Implement the menu button

Common functions of the editor include: create, open, save, copy, paste, cut, etc. In order to implement these functions, we need to create corresponding menu buttons. The code to add a menu button to HTML is as follows:

<button onclick="newFile()">新建</button>
<button onclick="openFile()">打开</button>
<button onclick="saveFile()">保存</button>
<button onclick="copyText()">复制</button>
<button onclick="pasteText()">粘贴</button>
<button onclick="cutText()">剪切</button>

It should be noted here that the onclick function is called through JavaScript.

3. Implement the functions in the editor

1. New file function

The new file function actually clears the value of the text box. Implemented through the following code:

function newFile() {
  document.getElementById("editor").value = "";
}

2. Open file function

The essence of the open file function is to read the local file text into the text box for editing. Since JavaScript cannot directly access the local file system, we need to select the file via <input type="file">. The following is the code implementation for opening a file:

function openFile() {
  var fileInput = document.createElement("input");
  fileInput.type = "file";

  fileInput.addEventListener("change", function () {
    var file = fileInput.files[0];
    var reader = new FileReader();

    reader.onload = function () {
      document.getElementById("editor").value = reader.result;
    }

    reader.readAsText(file);
  });

  fileInput.click();
}

It should be noted here that the FileReader API allows us to read files directly on the client without uploading them to the server.

3. Save file function

The essence of the save file function is to download the text in the text box to the local computer and save it as a specified file name. The following is the code for the save file function:

function saveFile() {
  var element = document.createElement("a");
  var text = document.getElementById("editor").value;
  var file = new Blob([text], { type: 'text/plain' });

  element.href = URL.createObjectURL(file);
  element.download = "filename.txt";
  element.click();
}

The Blob object and the URL.createObjectURL() method are used here. A Blob object is used to represent an immutable, raw data file-like object. The URL.createObjectURL() method creates a URL from a Blob object.

4. Copy, paste and cut functions

These three functions operate the content in the text box and are implemented in similar ways. Here we take the copy function as an example:

function copyText() {
  document.execCommand("copy");
}

The document.execCommand() function is used here to execute a custom command.

4. Implement shortcut keys

Shortcut keys are one of the common functions of the editor, which can improve operating efficiency. Five shortcut keys are implemented below:

document.onkeydown = function (event) {
  if (event.ctrlKey && event.keyCode === 78) { // CTRL + N
    newFile();
  } else if (event.ctrlKey && event.keyCode === 79) { // CTRL + O
    openFile();
  } else if (event.ctrlKey && event.keyCode === 83) { // CTRL + S
    event.preventDefault();
    saveFile();
  } else if (event.ctrlKey && event.keyCode === 67) { // CTRL + C
    copyText();
  } else if (event.ctrlKey && event.keyCode === 86) { // CTRL + V
    pasteText();
  } else if (event.ctrlKey && event.keyCode === 88) { // CTRL + X
    cutText();
  }
}

In the above code, event.ctrlKey and event.keyCode determine the Ctrl and key code of the key respectively.

5. Summary

The above code implements a simple text editor through JavaScript, including common functions such as creating, opening, saving, copying, pasting, and cutting. As programming enthusiasts, we can expand more functions based on this, and even implement a complete code editor.

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