title: Javascript - Can't push an array to 2D array
body: <p>I read a file line by line, turn each line into an array of number and push that array to a 2D array. But when I logged that 2D array, it was empty. I really don't know what's wrong here.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>var readline = require('readline');
  var fs = require('fs');
  
  var interface = readline.createInterface({
      input: fs.createReadStream('dataset.csv')
  });
  
  var transactions = []; // declare the 2d array
  interface.on('line', function (line) {
      var str = line.trim().split(' ').map(Number); // turn each line to a number array
      transactions.push(str); // push that number array to the 2d array
  });
  
  console.log(transactions);
  </code></pre>