Comparing strings, returned from php, in jQuery doesn't work

Question

I am returning a string form php and compare it with another string in jQuery. I am 100% certain that the strings do match (well, at least are of the same value...), but still my if-clause thinks otherwise.

This is the part of my php-script that sets the returning value:

if (!$result){
        echo "false";
        exit();
    }

This is my jQuery that performs the matching:

$.post("registeraccount.php",$(this).serialize(),function(msg){
        //alert the response from the server
        alert(msg + " = " + (msg == "false"));
        if(msg == "false"){
            $("#adminarea").html("Error");

        }else{
            $("#adminarea").html("Success");
        }

   });

No matter that the strings are equal or not equal, it's always "Success" that is printed on the web page.

In the alert I get the following result "false = false". Hence, (msg == "false") is false.

How come the strings are not true when they are equal and how do I fix it?

@silverstrike, doesn't 'echo "false"' imply that it is a string? — Nicsoft
– Nicsoft, Commented Aug 7, 2011 at 7:26
Not necessarily. The server echo the word false, but do you pass false or "false"? — silverstrike
– silverstrike, Commented Aug 7, 2011 at 7:33

sergio · Accepted Answer · 2011-08-07 07:24:29Z

4

I suppose that the reason is that msg, your server output, is never exactly "false", due to some line endings that are added or similar things in you PHP script (you could check if msg has the length you expect to verify this hypothesis). In this case, you could try using this:

 if (msg.match(/false/)) {

which does a somewhat less strict comparison if you want, ensuring that the output contains the string "false" (at any position). If it works, I suggest that you use instead this comparison:

 if (msg.match(/^false$/)) {

which guarantees that false be a whole line of your text.

answered Aug 7, 2011 at 7:24

sergio

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2 Comments

Peter Ajtai Over a year ago

or if ($.trim(msg) == "false") { or if (msg.indexOf('false') > -1) {

Nicsoft Over a year ago

@sergio, msg.match(/false/) worked but msg.match(/^false$/) didn't. Thanks!

Brad Mace · Accepted Answer · 2011-08-08 05:07:02Z

-3

You have to use === to compare for equality in JavaScript.

If you have time have a look at Crockford video series on javascript. It covers this and a lot of other javascript topics.

edited Aug 8, 2011 at 5:07

Brad Mace

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answered Aug 7, 2011 at 7:22

Dauleone

1

1 Comment

Nicsoft Over a year ago

Didn't work. I don't think it should be necesseary, should it? Googling around for comparing strings in javascript, most posts say "==".

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