递归函数中的变量声明

Question

I spent a long time trying to complete this function only to see that the syntax i was trying was not being accepted.

The countSheep function in code academy tells you to complete the function and gives you a newNumber variable that seems to not be defined in the local scope. So I tried to give it the "var" keyword. For some reason I can't understand the var keyword was not necessary and in order to complete the function and get it to pass the test I had to use the following:

as opposed to defining the variable I just used newNumber = number -1; // can also be written as newNumber -= 1; passed newNumber to the function

OR

not defined the newNumber variable and just invoke the function using n-1 as the parameter.

Here is the code that code academy gave us to solve.

 function countSheep(number) { if (number === 0) { console.log("Zzzzzz");// Put your base case here } else { console.log("Another sheep jumps over the fence."); // Define the variable newNumber as // 1 less than the input variable number newNumber = number - 1; // Recursively call the function // with newNumber as the parameter countSheep(newNumber); } } 

Can someone please tell me why the var keyword is not necessary inside of the function to define the newNumber variable. I appreciate it.

Answer 1

if you declare newNumber using var it is only accessable on the scope of else block

.But if you don`t use var it will not be local,means can be accessed on the outer scope**(countSheep).**

Answer 2

newNumber is a global variable that means, it is assigned to the global object. In browsers this is the window object:

 function f(x) { y = x; } console.log(window.y); f(123); console.log(window.y); 

To create a local variable that is only accessible within the function, use var :

 function f(x) { var y = x; console.log("within f:", y); } f(123); console.log("outside f:", window.y); 

To create a local variable that is only accessible within its surrounding block, use let or const :

 function f(x) { { let y = x; console.log("inside block", y); } try {y} catch (e) {console.log("outside block:", e.message)} } f(123);