How are absolute or relative file paths of the custom modules resolved in node.js?

Question

require doesn't seem to take any path other than './parser1' . I have placed both the js files in Desktop. I ran node my_parser.js , it always threw me an error saying "Cannot find module" for relative path require('parser1') or absolute path require('Desktop/parser1').

Why does it resolve the file path only with require('./parser1' ? What is the configurations behind it?

Please find the code below:

 // Require my new parser.js file.
var Parser = require('./parser1');

var fs = require('fs');

// Read the contents of the file into memory.
fs.readFile('Desktop/example_log.txt', function (err, logData) {

// If an error occurred, throwing it will
  // display the exception and end our app.
  if (err) throw err;

// logData is a Buffer, convert to string.
  var text = logData.toString();

  // Create an instance of the Parser object.
  var parser = new Parser();

  console.log(parser.parse(text));
});

parser1:

// Parser constructor.
var Parser = function() {

};

// Parses the specified text.
Parser.prototype.parse = function(text) {

var results = {};

// Break up the file into lines.
  var lines = text.split('\n');

lines.forEach(function(line) {
    var parts = line.split(' ');
    var letter = parts[1];
    var count = parseInt(parts[2]);

if(!results[letter]) {
      results[letter] = 0;
    }

results[letter] += parseInt(count);
  });

return results;
};

// Export the Parser constructor from this module.
module.exports = Parser;

Answer 1

require(..) can be used with one of two path types:

• path relative to current fle
• name of installed package

Relative path:

Relative path begins with a dot + slash ( './' ) and then you put actual relative position of required file: ./path/to/your/module

Installed package name

If, on the other hand you choose to use require directly with package name, eq. require('express') , node looks for a specific folder that keeps installed modules: node_modules . Once it finds matching one, it is imported. If none of the packages match, node tries to find another node_modules folder one level above in your OS file system. If it fails to find anything, it raises the error you've got.