Javascript object becomes undefined in a for loop

Question

When I am trying to add the usersData object to the filter idToName inside the for loop, it suddenly becomes undefined. Shouldn't the usersData get the value before the for loop runs? How should I fix it?

  Project.getProjects()
  .success(function(data) {
    vm.projects = data;
    var projectLength = vm.projects.length;

    // Get usersData
    User.allUsers()
    .success(function(data) {
      usersData = data;
      console.log(usersData); // It prints the object
    })

    for (var i = 0; i < projectLength; i++){
      console.log(usersData); // It prints undefined
      vm.projects[i].assigneeID = $filter('idToName')(vm.projects[i].assigneeID, usersData);
    }
  })

The success callback has not executed when the for loop runs. — zzzzBov, Aug 13 '15 at 17:20

score 3 · Accepted Answer · answered Aug 13 '15 at 17:17

It must be due to async calls. Try updating your code to following

// Get usersData
    User.allUsers()
    .success(function(data) {
      usersData = data;
      console.log(usersData); // It prints the object
      for (var i = 0; i < projectLength; i++){
          console.log(usersData); // It prints undefined
           vm.projects[i].assigneeID = $filter('idToName')(vm.projects[i].assigneeID, usersData);
      } 
    })

score 2 · Answer 2 · edited Jun 23 '16 at 14:33

2

Move the for loop to inside the callback for the User.allUsers call. You're consuming the usersData before object is returned!

edited Jun 23 '16 at 14:33

Nikhil Aggarwal

28,197
4
43
59

answered Aug 13 '15 at 17:17

Michael Tang

4,686
5
25
24

'Consuming the object' is a pretty inaccurate and confusing thing to say about a variable scope issue. – pvg Aug 13 '15 at 17:19
It's more of a (deterministic) race condition than a scoping issue. As far as we can tell, `usersData` is scoped globally. – Michael Tang Aug 13 '15 at 17:21

Javascript object becomes undefined in a for loop

2 Answers2