如何在npm包函数中创建全局变量

Question

Im using npm papercut https://www.npmjs.com/package/papercut and I want to get access to a variable value that is within a papercut function. This is what I have so far.

I want to get access to the value of the variable Img outside the function to the variable NewImg here Im trying to do so using a global variable. Anyone see my problem or have any suggestions.

 var NewImg = {} uploader.process('image1', file.path, function(images){ var Img = images.avatar NewImg.input = Img console.log(Img); }) console.log(NewImg.input) 

this logs out undefined

Answer 1

Looks like some asynchronous code. It's likely that the callback isn't called before your console.log() so your NewImg.input is undefined.

Also var NewImg.input = Img is not syntactically correct, remove var .

UPDATE

Read more about asynchronous javascript: Asynchronous Javascript

var NewImg = {}

uploader.process('image1', file.path, function(images){
  // I'm a callback function in an asynchronous method!
  // I will run sometime in the future!
  var Img = images.avatar
  NewImg.input = Img
  console.log(Img);
})
// Oh no! I ran before the callback function in the *asynchronous* method above, before NewImg.input is assigned any value
console.log(NewImg.input) 

Answer 2

If you use var inside a function, then you make new variable inside the function with the same name. So your code should be:

var NewImg = {}

uploader.process('image1', file.path, function(images){
  var Img = images.avatar;
  NewImg.input = Img;
  console.log(Img);
  console.log(NewImg.input) 
})