How to read files present in array nodejs

Question

I would like to know to read the files and search for keyword sample in nodejs.

If keyword found, display the path

const allfiles = [
  'C:\\Users\\public',
  'C:\\Users\\public\\images',
  'C:\\Users\\public\\javascripts\\index1.js',
  'C:\\Users\\public\\javascripts\\index2.js'
]


const readFile = (path, opts = 'utf8') =>
  new Promise((resolve, reject) => {
   try{
      let result=[];
      fs.readFile(path, opts, (err, data) => {
        if (err) reject(err)
        else {
          if(data.indexOf("sample")>=0){
             result.push(data);
             resolve(result);
          }
        }
      })
    }
    catch (e) {
      console.log("e", e);
     }
  })

  const run = async () => {
    allfiles.forEach(e=>{
      const s = await readFile(e);
      console.log(s);
    })
  }
run();

Expected Output
[
  'C:\\Users\\public\\javascripts\\index1.js',
  'C:\\Users\\public\\javascripts\\index2.js'
]

Does the order of the results matter? Do you have an inclination as to where the keyword will mostly likely be in the file? How big are the files? — James
– James, Commented Feb 21, 2021 at 8:49
@James thanks for reply, there is no order of results, no inclination of keyword, small file — ved
– ved, Commented Feb 21, 2021 at 8:53

Adam Zerner · Accepted Answer · 2021-02-22 02:32:54Z

2

Some tips:

What happens when "sample" isn't found in readFile?
You're currently pushing the data into result instead of the path.
Think about what you're trying to accomplish with readFile. To me, what you want to do is see if that file has the word "sample", and return true if so and if not return false. So I'd name the function checkIfFileHasSample and have it return a boolean. Then in your run function, in the forEach you have the path, so that is where I'd add the path to a list of results.
Maybe you already realized this, but run is never actually called in your code sample. Ie. run() doesn't happen.

Solution:

You had some syntax errors and a tricky gotcha with async-await with run. For the syntax errors, it'll come with experience, but I'd also recommend using ESLint to help you catch them, as well as making sure your code is always properly indented.

const fs = require("fs");
const allfiles = [
  "C:\\Users\\public",
  "C:\\Users\\public\\images",
  "C:\\Users\\public\\javascripts\\index1.js",
  "C:\\Users\\public\\javascripts\\index2.js",
];

const checkIfFileHasSample = (path, opts = "utf8") =>
  new Promise((resolve, reject) => {
    fs.readFile(path, opts, (err, data) => {
      if (err) {
        reject(err);
      } else {
        if (data.includes("sample")) {
          resolve(true);
        } else {
          resolve(false);
        }
      }
    });
  });

const run = async () => {
  const results = [];

  for (let i = 0; i < allFiles.length; i++) {
    try {
      const file = allFiles[i];
      const hasSample = await checkIfFileHasSample(file);

      if (hasSample) {
        results.push(file);
      }
    } catch (e) {
      console.log(e);
    }
  }

  console.log(results);
};
run();

edited Feb 22, 2021 at 2:32

answered Feb 21, 2021 at 8:34

Adam Zerner

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2 Comments

ved Over a year ago

thanks a lot for helping, but getting error

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: EISDIR: illegal operation on a directory,

Adam Zerner Over a year ago

Whoops, I forgot the try-catch. I updated my code to include it. See developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… for why it's needed. That won't solve your root problem though. illegal operation on a directory sounds like there's a problem with fs.readFile. It worked for me, so it's probably that your file paths are wrong.

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