Find a string

Question

I have the following Javascript function:

document.addEventListener("DOMContentLoaded", function(){
  document.getElementById('file').onchange = function() {

  var extPermitidas = ['txt'];
  var extArquivo = this.value.split('.').pop();

  if(typeof extPermitidas.find(function(ext){ return extArquivo == ext; }) == 'undefined') {
    alert('O arquivo não pode ser validado pois possui extenção não permitida!');
    return;
  } else {
    var file = this.files[0];

    var reader = new FileReader();
    reader.onload = function(progressEvent){


      // By lines
      var lines = this.result.split('\n');
      for(var line = 0; line < lines.length; line++){
          console.log(lines[line]);
      }
    };
    reader.readAsText(file);
  }
  alert('Arquivo validado com sucesso!');
}});

If I have a file with lines more or less like this:

N3019283746536 9938 ANYTHING
N41092832938 01982108 81902

And I wish for example to check if your first 2 elements are N3 if your line size has 32 characters, how would I do that?

Answer 1

You can do it with the method .susbtr(0,2) (first two characters) and with .length (returns the string size).

Seria:

if(lines[line].substr(0,2) == "N3" && lines[line].length == 32){
   // atendeu às condições
}

Note that I used the operator && which make the two conditions of if.