Check if a number is in between of two number in javascript / jquery

between.js

Number.prototype.between  = function (a, b) {
    var min = Math.min.apply(Math, [a,b]),
        max = Math.max.apply(Math, [a,b]);
    return this > min && this < max;
};

var windowSize = 550;

console.log(windowSize.between(500, 600));

// Result 
//true