Initializing Javascript Object at zero?

Question

Is there a way to initialize a object with zero the way you can initialize a hash in ruby with 0 value?

Hash.new(0)...Object.create(0)?

I am trying to itterate thru an array and add each element as a key and increment the values.

6502 · Accepted Answer · 2014-12-13 07:20:08Z

4

No.

But you can do things like

tab[key] = (tab[key] || 0) + 1;

Having a default value would be slightly nicer but it wouldn't work when the default needs to be an expression to be evaluated only if needed.

With this pattern instead you can easily do things like

return cache[key] || (cache[key] = new Machine(...));

edited Dec 13, 2014 at 7:20

answered Dec 13, 2014 at 7:12

6502

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Comments

Amir Popovich · Accepted Answer · 2014-12-13 07:13:31Z

2

You can always create an Array with a default value using apply and map:

var arrSize = 10;
var arr = Array.apply(null, new Array(arrSize)).map(Number.prototype.valueOf,0);
console.log(arr); // [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

answered Dec 13, 2014 at 7:13

Amir Popovich

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Comments

Todd · Accepted Answer · 2014-12-13 07:46:16Z

-1

if you're trying to create an empty object you can just:

var obj = {};

Here's some stuff that wasn't asked for to deter downvotes

var obj = {};
['Lorem', 'ipsum', 'dolor', 'sit', 'amet,', 
 'consectetur', 'adipisicing', 'elit.', 'Enim', 
 'nam', 'aperiam,', 'doloribus', 'dolor', 'ullam', 
 'corrupti', 'aliquid', 'Magni', 'consequuntur', 
 'velit', 'consectetur', 'autem', 'sit', 'sint',
 'temporibus', 'inventore'].forEach(function(a, i) {
    obj[a] = i;
});
console.log(JSON.stringify(obj, null, 4));

edited Dec 13, 2014 at 7:46

answered Dec 13, 2014 at 7:29

Todd

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3 Comments

Todd Over a year ago

I think you missed the location of the questionmark.

T J Over a year ago

That was either to encourage improving/ deleting the answer. Now I'll take it back ;)

Juan Over a year ago

Initializing with zero (original question) is not the same as creating an empty object. Please revisit your answer.

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