Multiple comparison operators in a JavaScript boolean expression

Question

I\'m trying to check whether the variable y is less than x and greater than z, but this boolean expression is returning false for some reason. Does JavaScript allow boolean

Answer 1

Change your test to

if (x > y && y > z){

When you write (x > y > z), this is equivalent to ((x>y)>z), so you're comparing a boolean (x>y) to z. In this test, true is converted to 1, which isn't greater than 2.

Answer 2

Try using the logical and operator:

if (x > y && y > z) {

to guarantee both conditions are true.

DEMO: http://jsfiddle.net/3sxvy/

If you need to put this into a function, you could try:

function compareNumbers(direction) {
    var inOrder = (function () {
        if (direction === "desc") {
            return function (current, before) {
                return current <= before;
            };
        } else if (direction === "asc") {
            return function (current, before) {
                return current >= before;
            };
        }
    })();
    var valid = true;
    for (var i = 2; i < arguments.length; i++) {
        if (!inOrder(arguments[i], arguments[i-1])) {
            valid = false;
            break;
        }
    }
    return valid;
}

if (compareNumbers("desc", 33, 5)) {
    console.log("Good");
} else {
    console.log("Bad");
}

DEMO: http://jsfiddle.net/kn6M4/1/

Answer 3

You want

if(x > y && y > z){
    alert("x > y > z"); //Nothing happens!
}

Javascript will try to parse your original statement from left to right and you'll end up comparing z to a boolean value which will then be parsed to a number (0 or 1).

So your original statement is equivalent to

if( (x > y && 1 > z) || (x <= y && 0 > z))