Unable to compare two Strings in javascript

问题

I am trying two compare two strings in JavaScript. But I guess there is some problem while comparing. It doesn't show the results.

if(ajaxRequest.readyState == 4){

    var msg = ajaxRequest.responseText;
    var fld = document.getElementById("prtCnt");
    if(msg == "false") {
        var msg = "This User Name is already taken !!!!";
        fld.className = "bp_invalid";
        //   fld.style.color=green;
        fld.innerHTML=msg;
    }

Can any body tell me where the problem is? Thanks.

回答1:

You might want to check if there's any space before or after the "false" string that you return from the server. You can do it easily with this:

alert('"' + msg + '"');

If there is extra space, you can just do:

msg = msg.trim();

and then do your if statement

回答2:

Ensure that there is no white space around the word "false" with something like:

if( msg.match(/\s*false\s*/i) )

来源：https://stackoverflow.com/questions/9543633/unable-to-compare-two-strings-in-javascript