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 expressions to be written concisely like this? If so, what is the correct syntax?
x = 2;
y = 3;
z = 4;
if(x > y > z){
alert("x > y > z"); //Nothing happens!
}
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");
}
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.
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))
if(true > z) { which makes no sense. The same mechanism that would allow your example to be more concise would not allow things like var x = y || z || g; which is a greater benefit than syntactical sugar.