JQuery if带有负值和正值的语句

Question

I got two variables in a function: $x= -660px and is fixed and $y which is reduced by 20px each time the function is called. $y = 220px the first time the function is called.
In the function I got an if else statement

    if($y > $x){
    //do something
    }else{
    //do nothing
    }

What I'm trying to get is for $y to be reduced as long as its bigger than -660px and then stop.

it works fine until $y = -20px. ie. the if statement 'does something' until $y = -20px and then it stops but doesn't execute the 'else' statement.

I can't find out what's wrong with it. Is this correct or might my problem come from somewhere else?

---

Answer 1

Shouldn't it be if($y < $x) since they are negative values?

This works:

$(function(){
    var x=0,y=-660;
    var inter = setInterval(function(){
        if(y < x)
            subtract();
        else
            clearInterval(inter);
    },200);
    function subtract(){
        x = x-20;
        $('body').append('<br />x='+x+' y='+y);
    }
});

DEMO

Working with px values:

$(function(){
    var x="0px",y="-660px";
    var inter = setInterval(function(){
        if(parseInt(y) < parseInt(x))
            subtract();
        else
            clearInterval(inter);
    },200);
    function subtract(){
        x = (parseInt(x)-20)+"px";
        $('body').append('<br />x='+x+' y='+y);
    }
});

DEMO