在JQuery中比较两个相同的字符串将返回false

Question

I discovered an interesting problem with an echoed value from an AJAX request of JQuery, which I don't have an answere for:

My data == "LOCKED" never returns true (line 13)!

JQuery -> AJAX call on button-click:

$.ajax({
        url: "ajax/login_ajax_call.php",
        method: "POST",
        data: { user: usr, password: pwd }
    }).done(function(data){
            if(data == true || data == "true"){          // -> this works with data beeing true (bool) or "true" (string)
                $("#form_submit").submit();
            }
            else{
                console.log(jQuery.type(data));          // -> (string)
                console.log(data);                       // -> "LOCKED" 
                console.log(jQuery.type("LOCKED"));      // -> (string)
                if(data == "LOCKED"){                    // also tried "===" but it never returns true
                    [...]            
                }
                else{
                    [...]
                }
            }
    }); 
});             

PHP (1) -> gets a value returned by a Class(PHP(2)):

include_once("../Classes/Login_check.php");
$lih = new Login_check();
$result = $lih -> check($_POST["user"], $_POST["password"]);
var_dump($result);                                     // -> string(6) "LOCKED"
echo $result;

PHP (2, "Login_check.php"):

[...]
// also tried: 
// $test = "LOCKED"; 
// var_dump($test);                                    // -> string(6) "LOCKED"
// return $test;
return "LOCKED";
[...]

Tell me if you need further informations! I hope anyone know what causes this problem!

Answer 1

Must be because of some white-spaces or new lines, it is always better to trim the data . Try this:

if (data.trim() == "LOCKED") {

You can also use:

if ($.trim(data) == "LOCKED") { // using jQuery.

Answer 2

You can try JSON.parse . If value looks like "LOCKED" on console, it means its like ""LOCKED"" .

Edit 1

As commented, you are getting "\\r\\nLOCKED" as stringified value, so you can use a regex to replace it. Following is the updated code.

Reference - How to remove all line breaks from a string?

Sample

 var a = "LOCKED"; var strA = "\\r\\nLOCKED"; var regex = /\\r?\\n|\\r/g; var cleanStr = strA.replace(regex,''); console.log(a); console.log(strA); console.log(strA == a); console.log(cleanStr == a); 

Answer 3

Probably due to whitepace somewhere, such as a space before an opening php tag etc.

Far better to use a structured data format like json, and return a boolean propery to avoid these issues:

$result = $lih -> check($_POST["user"], $_POST["password"]);
$locked = ($result == 'LOCKED');
header('Content-Type: application/json');
echo json_encode(['locked'=>$locked]);

Javascript:

if(data.locked){