未定义的变量？ 加密/解密

Question

Hey i am trying to make a simple encrypt/decrypt javascript. I am having a lot of trouble using variables from my first function into the second function.

the first function encrypts

2nd function decrypts

problem: I cannot use the variables I used in my first function. For example for "encoded" it keeps returning undefined! I attached my short code under.

 var encoded; function code(string, pass) { array=[] for (var i = 0; i<string.length; i++) { //converts code into an array & unicode b = (string.charCodeAt(i)) array.push(b) } //encovder let encoded = array.map(function(x) { return x*pass }) return encoded } (code("hello",7)) //decode function decoded() { console.log(encoded) } console.log(decoded())

Answer 1

You should assign the value of the function to your variable in the relevant scope:

var encoded;
function code(string, pass){
array=[]
for (var i = 0; i<string.length; i++){
//converts code into an array & unicode
b = (string.charCodeAt(i))
array.push(b)
}
//encovder
let encoded = array.map(function(x){
  return x*pass
})
return encoded
}
encoded = (code("hello",7));

By the way your result will be NaN because "hello".charCodeAt(5) is NaN and NaN * number == NaN .

Answer 2

Because you don't set the variable encoded that is defined on the first line, thus it value will be undefined when you try to log it.

WHY?

because inside code you redefine encoded on this line let encoded = ... and the later one shadows the one defined on the first line. So, here the second one gets set and not the first one (global one).

How to solve this?

You either not declare a new encoded inside the function (so this let encoded = ... should become this encoded = ... . Or assign the returned value of code to the global encoded like this var encoded = code("hello", 7); .

An example of Variable Shadowing :

 var value = 5; console.log(value); // uses the above value function foo(){ var value = 99; // redefining value (shadowing occur from this point) console.log(value); // logs the newly defined value. }// at this point, the value (99) gets destroyed. foo(); console.log(value); // logs 5 as it is the one belonging to this scope no matter wether the value (99) gets destroyed or not.

Read more about Scopes and Variable shadowing and Variables lifetime .