How to initialize an array with two empty objects in Javascript

Question

I am making an angular controller and need to initialize an array with two empty objects so that two lines will appear on the screen and I need to initialize a new object in the array when a + button is clicked. I am unsure about how to go about doing this.

This is my best attempt:

var myApp = angular.module('myApp', []);

myApp.controller('myController', ['$scope', '$q', function($scope, $q) {

    $scope.arr = [card('',''),card('','')];
    $scope.addLine = function(index){
        $scope.arr.push(card('',''));
    }
    $scope.removeLine = function(index){
        $scope.arr.splice(index, 1);
    }
}]);

function card(term, definition){
    this.term = term;
    this.definition = definition;
}

[new card('',''), new card('','')]

epascarello
– epascarello

2015-11-13 00:28:34 +00:00
Commented Nov 13, 2015 at 0:28 — epascarello
– epascarello, Commented Nov 13, 2015 at 0:28

Andreas Louv · Accepted Answer · 2015-11-13 00:34:33Z

2

You need to use the keyword new to make an instance of card:

$scope.arr = [new card('',''), new card('','')];
//            ^                ^ See new keyword  
$scope.addLine = function(index){
    $scope.arr.push(new card('',''));
    //              ^ See new keyword
}

Also you should consider always Capitalize your constructors (This way you can indicate that its an constructor:

new Card('', '');
function Card(...) {...}

You can also boil the need of the new keyword away by checking with instanceof:

// No need for new anymore:
var card = Card(1, 2, 3); 
console.log(card instanceof Card); // true
function Card(a, b, c) {
  if (!(this instanceof Card)) return new Card(a, b, c);
  this.a = a;
  this.b = b;
  // ...
}

answered Nov 13, 2015 at 0:34

Andreas Louv

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2 Comments

Mardymar Over a year ago

Good to know. Thanks.

Andreas Louv Over a year ago

@Mardymar Glad I could help :-) Because javascript cannot give you compile errors it's always a good idea have coding conventions to minimize the amount of unexpected errors.

Community · Accepted Answer · 2017-05-23 11:52:23Z

0

[new card('',''), new card('','')]

source

edited May 23, 2017 at 11:52

CommunityBot

11 silver badge

answered Nov 13, 2015 at 0:31

djechlin

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6 Comments

L3viathan Over a year ago

This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review

djechlin Over a year ago

@L3viathan yes it does. I don't know what more you could possibly want.

Drenmi Over a year ago

Please consider editing your post to add more explanation about what your code does and why it will solve the problem. An answer that mostly just contains code (even if it's working) usually wont help the OP to understand their problem.

ozil Over a year ago

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. - From Review

djechlin Over a year ago

@Drenmi if the OP is capable of reading the words then it will be clear how this source snippet answers the OP's problem. I'm sorry but I'm not writing a verbose answer just so it's easier to flip through posts in the "suspiciously short answer" queue and get your gold badge.

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