遞歸
遞歸函數是在函數通過調用自身的情況下構成的
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIiZpdmLlR2bjlHcvN2LcNHa0FGcjlGcfd3Xw9CXt92YuM3ZvxmYuNmLu9Wbt92Yvw1LcpDc0RHaiojIsJye.gif)
1 function factorial(num){2 if (num <=1){3 return 1;4 } else {5 return num * factorial(num-1);6 }7 }
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIiZpdmLlR2bjlHcvN2LcNHa0FGcjlGcfd3Xw9CXt92YuM3ZvxmYuNmLu9Wbt92Yvw1LcpDc0RHaiojIsJye.gif)
這是一個經典的遞歸階乘函數,但是下面的代碼會讓它出錯
1 var anotherFactorial = factorial;2 factorial = null;3 console.log(anotherFactorial(4));//factorial is not a function
在執行anotherFactorial()函數時,factorial已經不是函數了
arguments.callee是一個指向正在執行的函數的指針,是以何以用它來實作對函數的遞歸調用
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIiZpdmLlR2bjlHcvN2LcNHa0FGcjlGcfd3Xw9CXt92YuM3ZvxmYuNmLu9Wbt92Yvw1LcpDc0RHaiojIsJye.gif)
1 function factorial(num){2 if (num <=1){3 return 1;4 } else {5 return num * arguments.callee(num-1);6 }7 }
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIiZpdmLlR2bjlHcvN2LcNHa0FGcjlGcfd3Xw9CXt92YuM3ZvxmYuNmLu9Wbt92Yvw1LcpDc0RHaiojIsJye.gif)
但是在嚴格模式下,不能通過腳本通路arguments.callee,通路這個屬性會導緻錯誤。不過,可以使用命名函數表達式達成相同的結果
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIiZpdmLlR2bjlHcvN2LcNHa0FGcjlGcfd3Xw9CXt92YuM3ZvxmYuNmLu9Wbt92Yvw1LcpDc0RHaiojIsJye.gif)
1 var factorial = (function f(num){ 2 if (num <= 1){ 3 return 1; 4 } else { 5 return num * f(num -1); 6 } 7 }); 8 9 var anotherFactorial = factorial;10 factorial = null;11 console.log(anotherFactorial(4)); //24
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIiZpdmLlR2bjlHcvN2LcNHa0FGcjlGcfd3Xw9CXt92YuM3ZvxmYuNmLu9Wbt92Yvw1LcpDc0RHaiojIsJye.gif)