关于查找字符串和删除行的问题 - Node.JS

Question

Find string and delete line - Node.JS

var fs = require('fs')

fs.readFile('shuffle.txt', {encoding: 'utf-8'}, function(err, data) {
  if (err) throw error;

  let dataArray = data.split('\n'); // convert file data in an array
  const searchKeyword = 'user1'; // we are looking for a line, contains,       key word 'user1' in the file
  let lastIndex = -1; // let say, we have not found the keyword

  for (let index=0; index<dataArray.length; index++) {
    if (dataArray[index].includes(searchKeyword)) { // check if a line    contains the 'user1' keyword
      lastIndex = index; // found a line includes a 'user1' keyword
      break; 
    }
  }

  dataArray.splice(lastIndex, 1); // remove the keyword 'user1' from the data Array

  // UPDATE FILE WITH NEW DATA
  // IN CASE YOU WANT TO UPDATE THE CONTENT IN YOUR FILE
  // THIS WILL REMOVE THE LINE CONTAINS 'user1' IN YOUR shuffle.txt FILE
  const updatedData = dataArray.join('\n');
  fs.writeFile('shuffle.txt', updatedData, (err) => {
    if (err) throw err;
    console.log ('Successfully updated the file data');
  });

});

此链接说明如何查找字符串并删除行，但当时只删除一个 user1。我与 user1 有很多行，如何删除所有行：

john
doe
some keyword
user1
last word
user1
user1

反之亦然。如何删除所有行并只保留 user1 行？

Answer 1

我会使用Array.filter() 函数。

基本上，您在数组上调用filter()，并定义一个回调函数来检查该数组的每一项。

如果检查函数为特定项目返回true，请保留该项目 - 将其放入新数组 如果检查函数返回false，则不要将该项放入新数组中

因此，在您的情况下，一旦您将所有行读入一个数组（代码中的第 6 行），请使用 filter 函数：

// Delete all instances of user1
let newDataArray = dataArray.filter(line => line !== "user1")

// Delete everything except user1
let newDataArray = dataArray.filter(line => line === "user1")

// Delete any lines that have the text 'user1' somewhere inside them
let newDataArray = dataArray.filter(line => !line.includes("user1"))

然后，就像您在代码中所做的那样，在 newDataArray() 上使用 join() 函数并写入文件。

---

要重写你的代码，

var fs = require('fs')

fs.readFile('shuffle.txt', {encoding: 'utf-8'}, function(err, data) {
  if (err) throw error;

  let dataArray = data.split('\n'); // convert file data in an array
  const searchKeyword = 'user1'; // we are looking for a line, contains,       key word 'user1' in the file

  // Delete all instances of user1
  let newDataArray = dataArray.filter(line => line !== searchKeyword)

  // UPDATE FILE WITH NEW DATA
  const updatedData = newDataArray.join('\n');

  fs.writeFile('shuffle.txt', updatedData, (err) => {
    if (err) throw err;
    console.log ('Successfully updated the file data');
  });

});