Check For Uniqueness in Array, Push To Array if Unique

Question

Using AngularJS, I'm creating an addTodo function in my app.

I seem to be having trouble implementing a way to check the uniqueness of the object being added to the array, and having it followed by additional actions.

So far I'm able to get the additional actions working, but not the initial check for uniqueness. How can I implement the check for uniqueness action and then have it followed by the additional actions?

The addTodo function I'm trying to create flows like this (Bold means not implemented):

Check if todo is already in todos

1a. If it does exisit, don't push, display alert
Check if todo is not blank

2a. If it is blank, don't push, display alert
If unique and not blank, push to todos, display success message

Current addTodo function (without unqiueness check):

$scope.addTodo = function(){
  $scope.isVisible = true;
  if ($scope.todo) {
    $scope.todos.push($scope.todo);
    $scope.todo = '';
    $scope.alert = $scope.alerts[1];
  }else{
    $scope.alert = $scope.alerts[0];
  }
};

Note 1: $scope.alert and $scope.alerts are used to display certain error messages;

$scope.alerts[0]

"Please add text to your task."

$scope.alerts[1]

"Added a new task!"

The alert I want to display if the task being added already exists is

$scope.alerts[3]

"Task already in list."

Note 2: $scope.isVisible toggles the visibility of the alert

So todo is a simple string or an object?

Chandermani
– Chandermani

2013-08-18 11:10:48 +00:00
Commented Aug 18, 2013 at 11:10 — Chandermani
– Chandermani, Commented Aug 18, 2013 at 11:10
It's a simple string, yes

James Cliburn
– James Cliburn

2013-08-18 11:18:26 +00:00
Commented Aug 18, 2013 at 11:18 — James Cliburn
– James Cliburn, Commented Aug 18, 2013 at 11:18
Hope you have checked my answer then.

Chandermani
– Chandermani

2013-08-18 11:26:37 +00:00
Commented Aug 18, 2013 at 11:26 — Chandermani
– Chandermani, Commented Aug 18, 2013 at 11:26
I have, thank you! Adding a comment to it.

James Cliburn
– James Cliburn

2013-08-18 11:35:44 +00:00
Commented Aug 18, 2013 at 11:35 — James Cliburn
– James Cliburn, Commented Aug 18, 2013 at 11:35

rahulroy9202 · Accepted Answer · 2017-02-12 19:44:49Z

21

use Array.indexOf this way:

$scope.addTodo = function(){
  $scope.isVisible = true;
  if ($scope.todo) {
    if ($scope.todos.indexOf($scope.todo) == -1) {
        $scope.todos.push($scope.todo);
        $scope.todo = '';
        $scope.alert = $scope.alerts[1];
    }else{
     // $scope.todo is already in the $scope.todos array, alert the user
        $scope.alert = $scope.alerts[3];
    }
  }else{
    $scope.alert = $scope.alerts[0];
  }
};

edited Feb 12, 2017 at 19:44

rahulroy9202

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answered Aug 18, 2013 at 12:11

Mehdi

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2 Comments

James Cliburn Over a year ago

Fantastic, thank you! Solved my main issues of not being sure where in the flow to implement the action and how to properly implement it based on what I already had.

James Cliburn Over a year ago

Note for others: mef's flow differs from the flow I established above, but is actually the correct way to look at it: First, check if the todo is blank. If it isn't, THEN check if it is unique. My pitfall in the code below was I was too attached to the idea that I needed to check if the todo was unique first before checking if it was blank.

vinesh · Accepted Answer · 2015-11-18 12:48:25Z

2

if you are using underscore OR lodash, you can use this simple code to push unique items in array.

if (_.findWhere($scope.todos, $scope.todo) == null) {
    $scope.todos.push($scope.todo);
}

Hope this helps!!!

answered Nov 18, 2015 at 12:48

vinesh

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Comments

Chandermani · Accepted Answer · 2013-08-18 11:17:37Z

0

If you are using a standard string todo you can use the javascript array indexOf method. This method for object data types does a reference match.

Else you can also look at jquery grep method.

Use one of these methods to check if $scope.todos already contains such element and show the alert.

answered Aug 18, 2013 at 11:17

Chandermani

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1 Comment

James Cliburn Over a year ago

Based on that, I've edited the code like this, but it's still allowing duplicates to be pushed to the array;

$scope.addTodo = function(){ $scope.isVisible = true; var todos = $scope.todos; var todo = $scope.todo; if (todo == todos.indexOf(todo)){ $scope.alert = $scope.alerts[3]; } else if ($scope.todo) { $scope.todos.push($scope.todo); $scope.todo = ''; $scope.alert = $scope.alerts[1]; } else { $scope.alert = $scope.alerts[0]; } };

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