How to compare strings in JavaScript

Question

I want to compare two strings in JavaScript, but my code isn't working.

I think if(answer==correct_answer_arr[0]) is wrong, but I don't know what the problem is, or how I can fix it.

*I already checked that "correct_answer_arr" has no problem, which has correct information

JS Code:

var correct_answer_arr = new Array();

$('document').ready(function() {
  var str;
  var request = new XMLHttpRequest();
  request.open('get', 'http://localhost:8080/new/text.jsp', true);
  request.onload = function() {
    str = request.responseText;
    correct_answer_arr = str.split(",");
  };
  request.send();
});

function keycheck(event) {
  if (event.keyCode == 13) {
    var answer = $("input").val();
    if (answer == correct_answer_arr[0]) {
      alert("correct");
    } else {
      alert("wrong");
    }
  }
}

== will compare strings, what makes you think it is wrong? console.log both values to see if they are what you think they are — Patrick Evans
– Patrick Evans, Commented Sep 4, 2017 at 23:29
also $('document') won't select the document, it is $(document) — Patrick Evans
– Patrick Evans, Commented Sep 4, 2017 at 23:31
Do you only have one <input> on your page? The comparison will be 'wrong' if you don't have a valid answer in $("input").val(). — Obsidian Age
– Obsidian Age, Commented Sep 4, 2017 at 23:31

ledicjp · Accepted Answer · 2017-09-04 23:35:57Z

2

I would do console.log(correct_answer_arr); before and after the str.split(",") to see what's going on.

Please also check if answer get's set to undefined because it's a common error when calling $().val() on an empty collection. As already mentioned, document is a reserved keyword and should not be written in quotemarks in this case.

Also it's good practice to use === instead of ==.

answered Sep 4, 2017 at 23:35

ledicjp

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1 Comment

김진오 Over a year ago

i checked everything you said but my codes still doesn't work i think something happens when i get data with ajax.. string which is got with ajax has invisible control character?

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