Invalid left-hand side in assignment for simple login script

Question

I have to build a simple login script for a js class.

I cannot get the loop to work. Everytime I type in any info it gives me "Invalid left-hand side in assignment"

When the login button is clicked the getData function gets the values of the boxes then passes them to the logon function that checks against the array. That's where the script stops. If I change the = in the if statement to == it will accept the last valid login f the array but none of the others.

What am I doing wrong?

<script type="text/javascript">
var userLogins = [{user:"user1", password:"pass1"},{user:"user2", password:"pass2"},{user:"user3", password:"pass3"}]
var success = null;
function logon(user, pass) {
    userok = false;
    for (i = 0; i < userLogins.length; i++)
    { 
        if(pass = userLogins[i].password && user = userLogins[i].user )
        {
            success = true;
        }
        else
        {
            success = false;
        }
    }
    secret(success);
}

function getData() {
    var user = document.getElementById("userid").value;
    var password = document.getElementById("password").value;
    logon(user, password);
}

function secret(auth){
    if(auth)
    {
        show('success');
        hide('login');
    }
    else
    {
        show('error');
        hide('login');
    }
}

function show(show) {
    document.getElementById(show).className = "show";
}
function hide(hide) {
    document.getElementById(hide).className = "hide";
}

`=` is for assignments in JavaScript, you need to use `==` or `===`. — Fabrício Matté, Jan 30 '13 at 01:12

score 4 · Accepted Answer · edited May 23 '17 at 12:04

4

If I change the = in the if statement to == it will accept the last valid login f the array but none of the others.

= is the assignment operator

== is the equality operator

You're confusing the two. You want the latter. Otherwise, your assigning the value which results returns the value itself (often a true value).

Per the comments, there's also the strict equality operator. For the difference between == and === this answer will blow your mind.

edited May 23 '17 at 12:04

Community

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answered Jan 30 '13 at 01:11

Jason McCreary

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`===` to prevent coercion surprises – Matt Whipple Jan 30 '13 at 01:13
@Matt Whipple, indeed. Baby steps :) – Jason McCreary Jan 30 '13 at 01:13
I tried changing the `=` to `==` and `===` but the script only matches the last element in the array. user3 and pass3 work, but the others do not. – coryrwest Jan 31 '13 at 01:39
I guarantee you don't want to use `=`. How are you calling `logon(user, pass)`? You have another problem, unrelated to the `==`. – Jason McCreary Jan 31 '13 at 16:55

Invalid left-hand side in assignment for simple login script

1 Answers1