^_^判断奇偶

var isEven = function(n) {
    return !(n&1) // & 按位与
}
console.log(1, isEven(1))
console.log(25, isEven(25))
console.log(138, isEven(138))

var isEven = function(n) {
    return !!n.toString().match(/[02468]$/)
}
console.log(1, isEven(1))
console.log(25, isEven(25))
console.log(138, isEven(138))

var isEven = function(n) {
    return !(n % 2)
}
console.log(1, isEven(1))
console.log(25, isEven(25))
console.log(138, isEven(138))