Naming objects inside of an array dynamically

Question

I'm quite new to JavaScript and programming in general and figured I'd hone my abilities by working on a small project. The idea is that I have a form for information on an event, an input for the name, date, time and a small thumbnail image.

I want each event to be an object inside of an array, so I would have something like:

var concerts = {};

for (var i = 1; i < 11; i++) {
    window["concert"+i] = new Object();
}

and the array would end up being something:

var concerts = [concert1, concert2, concert3]

and so on.

How could I get this loop to work so that it would take the 3 parameters and create a new object in the array named 'concert'+i? Thanks for reading!

Take 3 parameters from where?

doctorlove
– doctorlove

2017-05-08 10:56:42 +00:00
Commented May 8, 2017 at 10:56 — doctorlove
– doctorlove, Commented May 8, 2017 at 10:56

Jonas Wilms · Accepted Answer · 2017-05-08 10:58:06Z

3

Concerts must be an array:

var concerts = [];

for (var i = 0; i < 10; i++) {
  concerts[i] = {
    //maybe also giveit a name if you want to:
    name:"concert"+i
  };
}

You can access it like this:

concerts[0].name="Wacken";//first concert...

Note that this:

window["concert"+i] = new Object();

is very bad style...

answered May 8, 2017 at 10:58

Jonas Wilms

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Comments

cezar · Accepted Answer · 2017-05-08 11:20:38Z

0

First you declare a variable concerts of type object. But you want an array. That first line makes your code very confusing.

You have to start with an empty array:

var concerts = []; // alternatively: new Array();

In the end you'd like to have a structure like this:

[
    { /* object 1 */ },
    { /* object 2 */ }
]

Now you can run a foor-loop and populate the array:

for (var i = 0; i <= 10; i++) {
    concerts.push({['concert' + i]: {}});
}

This will return something like:

[
    {'concert0': {}},
    {'concert1': {}},
    // skipped
    {'concert10': {}}
]

Later you can populate the objects. This is however not a very nice style. Maybe you should reconsider if it is really necessary to give a name to every object like concert0...10.

Go rather for:

var concerts = [
    {
        'name': 'concert0',
        'location': 'somewhere'
    }
    // continue with other objects
];

answered May 8, 2017 at 11:20

cezar

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3 Comments

cezar Over a year ago

@Jonasw Thanks for the comment! Array can't be a key in a JavaScript object. This expression however is not an array. The part ['concert' + i] returns a string - 'concert' is string and i is number. Due to the type coercion in JS the result is a string, returned by the square brackets. Otherwise you couldn't create dynamically the key names in a foor loop.

Jonas Wilms Over a year ago

oh sorry, ive already forgot that... :/ maybe because i think that dynamic keys are a generally bad idea...

cezar Over a year ago

I think, too, that dynamic keys are a very bad idea. It's what the OP wanted. In JavaScript you can call a value of an object with a dot notation or with square brackets: var o.name = 'Jonas'; or var o['name'] = 'Jonas';. The key in the square brackets can be generated by some operation: var o['n' + 'am' + 'e'] = 'Jonas';. In my answer it looks really weird, that is why I suggest in the end to go for another solution.

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