Unexpected token u in JSON at position 0 - angularjs

Question

when I'm try to convert string to object I get error ``:
Unexpected token u in JSON at position 0
Service
setUser : function(aUser){
//sauvegarder User
localStorage.setItem('User', JSON.stringify(aUser));
},
getUser : function(){
//récuperer User
return JSON.parse(localStorage.getItem('User'));
}

Answer 1

The first thing to do is to look at what you're trying to parse. My guess is that you'll find it's "undefined", which is invalid JSON. You're getting undefined because you haven't (yet) saved anything to that key in local storage. undefined is then converted to the string "undefined" which JSON.parse can't parse.
I usually store and retrieve things in local storage like this:
Storing (just like yours):
localStorage.setItem("key", JSON.stringify(thing));
Retrieving (this is different):
thing = JSON.parse(localStorage.getItem("key") || "null");
if (!thing) {
// There wasn't one, do whatever is appropriate
}
That way, I'm always parsing something valid.

Answer 2

You are getting this error because you are not returning the response as a JSON string while your browser is expecting a JSON string to parse. Hence it is taking the first letter of your response string and throwing an error.
You can verify it by going to the networking tab of your browser's Dev tools and viewing the response.
To resolve this issue, you can use the code below in your http request.
var promiz = $http.post(url, data, {
transformRequest: angular.identity,
transformResponse: angular.identity,
headers: {
'Content-Type': undefined
}
});
Hope this helps!

Answer 3

I was also getting the same error. The problem was the response I was getting from HTTP Get Request was not in JSON format, Instead it was plain text.
this.BASE_URL = "my URL";
public getDocument() {
return this.http.get(this.BASE_URL)
.map((res: Response) => res.json())
.catch((error: any) => Observable.throw(error.json().error || 'Server error'));
}
So, the JSON Parser was throwing an error.
When I map it into plain text like this:
.map((res: Response) => res.text());
It works.