Node.js fs.unwatchFile()用法及代碼示例

fs.unwatchFile()方法用於停止監視給定文件的更改。可以指定一個可選的偵聽器參數，以僅從文件中刪除指定的偵聽器。否則，將刪除與該文件關聯的所有偵聽器。如果使用此函數時未監視文件，則它將不執行任何操作並引發任何錯誤。

用法:

fs.unwatchFile(filename[, listener])

參數：該方法接受上述和以下所述的兩個參數：

filename:它是一個String，Buffer或URL，表示必須停止監視的文件。
listener:該函數指定以前使用fs.watchFile()函數附加的偵聽器。如果指定，則僅刪除此特定的偵聽器。它是一個可選參數。

以下示例說明了Node.js中的fs.unwatchFile()方法。

範例1：

// Node.js program to demonstrate the  
// fs.unwatchFile() method 
  
// Import the filesystem module 
const fs = require('fs'); 
  
// Start watching the file 
fs.watchFile("example_file.txt", (curr, prev) => { 
  console.log("\nThe file was edited"); 
  
  console.log("Previous Modified Time:", prev.mtime); 
  console.log("Current Modified Time:", curr.mtime); 
}); 
  
// Make Changes to the file before  
// it has been stopped watching 
setTimeout( 
  () => fs.writeFileSync("example_file.txt", 
         "File Contents are Edited"), 
  1000 
); 
  
// Stop watching the file 
setTimeout(() => { 
  fs.unwatchFile("example_file.txt"); 
  console.log("\n> File has been stopped watching"); 
}, 6000); 
  
// Make Changes to the file after 
// it has been stopped watching 
setTimeout( 
  () => fs.writeFileSync("example_file.txt", 
          "File Contents are Edited Again"), 
  7000 
);

輸出：

The file was edited
Previous Modified Time:2020-05-30T08:43:28.216Z
Current Modified Time:2020-05-30T08:43:37.208Z

File has been stopped watching

範例2：

// Node.js program to demonstrate  
// the fs.unwatchFile() method 
  
// Import the filesystem module 
const fs = require('fs'); 
  
// Defining 2 listeners for watching the file 
let listener1 = (curr, prev) => { 
  console.log("Listener 1:File Modified"); 
}; 
let listener2 = (curr, prev) => { 
  console.log("Listener 2:File Modified"); 
}; 
  
// Using both the listeners on one file 
fs.watchFile("example_file.txt", listener1); 
fs.watchFile("example_file.txt", listener2); 
  
// Modify the file contents 
setTimeout( 
  () => fs.writeFileSync("example_file.txt", 
          "File Contents are Edited"), 
  1000 
); 
  
// Stop using the first listener 
setTimeout(() => { 
  fs.unwatchFile("example_file.txt", listener1); 
  console.log("\n> Listener 1 has been stopped!\n"); 
}, 6000); 
  
// Modify the file contents again 
setTimeout( 
  () => fs.writeFileSync("example_file.txt", 
          "File Contents are Edited Again"), 
  8000 
);

輸出：

Listener 1:File Modified
Listener 2:File Modified

Listener 1 has been stopped!

Listener 2:File Modified

參考： https://nodejs.org/api/fs.html#fs_fs_unwatchfile_filename_listener

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注：本文由純淨天空篩選整理自sayantanm19大神的英文原創作品 Node.js | fs.unwatchFile() Method。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。