javascript
function isEven(number){
if(number===0)
return true
else if(number===1)
return false
return isEven(number + (number > 0 ? -2 : 2))
}
console.log(isEven(50));
// → true
console.log(isEven(75));
// → false
console.log(isEven(-1)); /** 负数会导致超出最大调用堆栈 */
// → ??