nodejs Node.js fs.existsSync()方法

Node.js fs.existsSync()方法

原文:https://www.geeksforgeeks.org/node-js-fs-existssync-method/

fs.existsSync()方法用于同步检查给定路径中是否已经存在文件。它返回一个布尔值，该值指示文件的存在。

语法:

fs.existsSync( path )

参数:该方法接受如上所述的单个参数，描述如下:

Path: Save the path of the file to be checked. It can be a string, a buffer or a web address.

返回值:如果文件存在，则返回布尔值，即真，否则返回假。

下面的程序说明了 Node.js 中的 fs.existsSync()方法:

例 1:

// Node.js program to demonstrate the
// fs.existsSync() method

// Import the filesystem module
const fs = require('fs');

// Get the current filenames
// in the directory
getCurrentFilenames();

let fileExists = fs.existsSync('hello.txt');
console.log("hello.txt exists:", fileExists);

fileExists = fs.existsSync('world.txt');
console.log("world.txt exists:", fileExists);

// Function to get current filenames
// in directory
function getCurrentFilenames() {
  console.log("\nCurrent filenames:");
  fs.readdirSync(__dirname).forEach(file => {
    console.log(file);
  });
  console.log("\n");
}

输出:

Current filenames:
hello.txt
index.js
package.json

hello.txt exists: true
world.txt exists: false

例 2:

// Node.js program to demonstrate the
// fs.existsSync() method

// Import the filesystem module
const fs = require('fs');

// Get the current filenames
// in the directory
getCurrentFilenames();

// Check if the file exists
let fileExists = fs.existsSync('hello.txt');
console.log("hello.txt exists:", fileExists);

// If the file does not exist
// create it
if (!fileExists) {
  console.log("Creating the file")
  fs.writeFileSync("hello.txt", "Hello World");
}

// Get the current filenames
// in the directory
getCurrentFilenames();

// Check if the file exists again
fileExists = fs.existsSync('hello.txt');
console.log("hello.txt exists:", fileExists);

// Function to get current filenames
// in directory
function getCurrentFilenames() {
  console.log("\nCurrent filenames:");
  fs.readdirSync(__dirname).forEach(file => {
    console.log(file);
  });
  console.log("\n");
}

输出:

Current filenames:
hello.txt
index.js
package.json

hello.txt exists: true

Current filenames:
hello.txt
index.js
package.json

hello.txt exists: true

参考:https://nodejs . org/API/fs . html # fs _ fs _ exists sync _ path