Javascript检查嵌套数组结构中的对象属性

Question

I have two main objects that I am dealing with here. One is called tasks that is an array of objects. The other is called userSelectedRoles which is an array of role ID's.

Within my tasks array, there is a property called Roles which is also an array of objects.

I am trying to see if the userSelectedRoles exist in any of the tasks, and if not, add them to it.

I created some pseudo I was trying to wrap my head around it.

Example:

var userSelectedRoles = [1, 2, 3],
  tasks = [{
    TaskName: 'Task 1',
    TaskID: 1,
    Roles: [{
      RoleName: 'Role1',
      RoleID: 1
    }, {
      RoleName: 'Role 2',
      RoleID: 2
    }]
  }, {
    TaskName: 'Task 2',
    TaskID: 2,
    Roles: [{
      RoleName: 'Role1',
      RoleID: 1
    }, {
      RoleName: 'Role 3',
      RoleID: 3
    }]
  }]


// Loop over our tasks
for (var t = 0; t < tasks.length; t++) {

  // Loop over the roles
  for (var r = 0; r < tasks[t].Roles.length; r++) {

    // Loop over our user selected roles
    for (var sr = 0; sr < userSelectedRoles.length; sr++) {

      // If this user selected role exists within our roles, continue
      if (tasks[t].Roles[r].RoleID == userSelectedRoles[sr]) {
        // This role exists, no need to do anything
      } else {
        // This user selected role does not exist in our tasks, we need to add it
        tasks[t].Roles.push({
          RoleName: 'Blah',
          RoleID: userSelectedRoles[sr]
        })
      }
    }

  }
}

The above code isn't working, crashed my fiddle so I assume I have a loop wrong somewhere.

Is there an easier way to do this without having to do all the loops perhaps?

The end goal here is that a new role would be added to both tasks. Task 1 = Role 3 & Task 2 = Role 2 .

Thoughts?

Answer 1

You could take a hash table and collect the id, you have. Then iterate the userSelectedRoles and if not set, then push the object to Roles .

 var userSelectedRoles = [1, 2, 3], tasks = [{ TaskName: 'Task 1', TaskID: 1, Roles: [{ RoleName: 'Role1', RoleID: 1 }, { RoleName: 'Role 2', RoleID: 2 }] }, { TaskName: 'Task 2', TaskID: 2, Roles: [{ RoleName: 'Role1', RoleID: 1 }, { RoleName: 'Role 3', RoleID: 3 }] }]; tasks.forEach(function (task) { var roleIds = Object.create(null); task.Roles.forEach(function (role) { roleIds[role.RoleID] = true; }); userSelectedRoles.forEach(function (id) { if (!roleIds[id]) { task.Roles.push({ RoleName: 'Blah', RoleID: id }); } }); }); console.log(tasks); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

ES6 with Set

 var userSelectedRoles = [1, 2, 3], tasks = [{ TaskName: 'Task 1', TaskID: 1, Roles: [{ RoleName: 'Role1', RoleID: 1 }, { RoleName: 'Role 2', RoleID: 2 }] }, { TaskName: 'Task 2', TaskID: 2, Roles: [{ RoleName: 'Role1', RoleID: 1 }, { RoleName: 'Role 3', RoleID: 3 }] }]; tasks.forEach(function (task) { var ids = new Set(task.Roles.map(({ RoleID }) => RoleID)); userSelectedRoles.forEach(id => ids.has(id) || task.Roles.push({ RoleName: 'Blah', RoleID: id })); }); console.log(tasks); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

Answer 2

How about doing it like this? (I always hated using for-loops, adds additional variables we don't need ie the index)

tasks.forEach(task => {
  var roleIds = task.Roles.map(r=>r.RoleID);
  userSelectedRoles.forEach( r => {
   if(roleIds.indexOf(r) === -1){
     task.Roles.push({RoleID: r, RoleName: 'blah'})
   }
  })
})

Answer 3

If you want to know where the mistake is... In the last loop, you add items to the Role. This means that the loop at 1 level higher will now make 1 more loop. And this loop will add a new role, which will make it loop one more time, wich will add one more role - I think you got it now :)

Solution using this same structure: store the length in a variable before starting the loop, and use that for the number of loops to do.

for (var t = 0; t < tasks.length; t++) {
  //CHANGED CODE START
  let rolesLength = task[t].Roles.length;
  // Loop over the roles
  for (var r = 0; r < rolesLength ; r++) {
    //CHANGED CODE END
    // Loop over our user selected roles
    for (var sr = 0; sr < userSelectedRoles.length; sr++) {

      // If this user selected role exists within our roles, continue
      if (tasks[t].Roles[r].RoleID == userSelectedRoles[sr]) {
        // This role exists, no need to do anything
      } else {
        // This user selected role does not exist in our tasks, we need to add it
        tasks[t].Roles.push({
          RoleName: 'Blah',
          RoleID: userSelectedRoles[sr]
        })
      }
    }

  }
}