javascript - 即使在进行更改后，Node js 也会在控制台中显示旧文件

Question

我正在读取一个文件并使用正常工作的 fs.watch 实时查找其中的更改。现在我想在每次文件更改时调用 app.get 。但我的函数“func_read_file_lines”仍在将旧文件发送回去。我找不到问题。

const express = require('express')
const app = express()
app.set('view engine', 'ejs');
var fs = require('fs');
const request = require('request');
require('log-timestamp');
path = require("path");
var filename = path.resolve('test.txt');
const buttonPressesLogFile = filename;


fs.watch(buttonPressesLogFile, (event, filename) => {
    if (filename && event === 'change') {
        console.log(`${filename} file Changed`);
        func_read_file_lines.
        then((data) => {
            let last_n_lines = data.split('\n').slice(-10, -1);
            console.log(last_n_lines)
        }).catch((err) => {
            console.log(err)
        })
    }
});

let func_read_file_lines = new Promise((resolve, reject) => {
    fs.readFile(filename, 'utf8', function read(err, data) {
        if (err) {
            console.log(err);
            reject(err);
        } else {
            resolve(data)
        }
    });
})
app.get('/', (req, res) => {
    func_read_file_lines.
    then((data) => {
        let last_n_lines = data.split('\n').slice(-10, -1);

        res.render('display', {
            last_n_lines: last_n_lines
        });

    }).catch((err) => {
        console.log(err)
    })
})


const port = 3000
app.listen(port, () => console.log(`Example app listening on port ${port}!`))

Answer 1

这是因为您只创建 func_read_file_lines 一次。尝试创建一个函数来返回 promise ，如下所示:

const express = require('express')
const app = express()
app.set('view engine', 'ejs');
var fs = require('fs');
const request = require('request');
require('log-timestamp');
path = require("path");
var filename = path.resolve('test.txt');
const buttonPressesLogFile = filename;


fs.watch(buttonPressesLogFile, (event, filename) => {
    if (filename && event === 'change') {
        console.log(`${filename} file Changed`);
        func_read_file_lines.
        then((data) => {
            let last_n_lines = data.split('\n').slice(-10, -1);
            console.log(last_n_lines)
        }).catch((err) => {
            console.log(err)
        })
    }
});

// CHANGE THE LINE BELOW
let func_read_file_lines = () => new Promise((resolve, reject) => {
    fs.readFile(filename, 'utf8', function read(err, data) {
        if (err) {
            console.log(err);
            reject(err);
        } else {
            resolve(data)
        }
    });
})
app.get('/', (req, res) => {
    func_read_file_lines(). // CHANGED THIS LINE
    then((data) => {
        let last_n_lines = data.split('\n').slice(-10, -1);

        res.render('display', {
            last_n_lines: last_n_lines
        });

    }).catch((err) => {
        console.log(err)
    })
})


const port = 3000
app.listen(port, () => console.log(`Example app listening on port ${port}!`))