how to Initialize a Javascript Array with non-zero index

Question

I'm passing an array to a function and I'm curious if there is a quick way to use the json style array initializer to pass an anonymous array:

e.g.:

myfunction([1,2,3,4]);

Is there some special syntax in javascript that would allow one to initialize the array with non-zero index?

for example, instead of

myfunction([,,,,4321]);

//array[4] == 4321 here

but if you have an array that has the first 100 positions undefined, you would have to have 100 commas. [,,....,4321]

basically looking for a short form for:

var a = new Array(); a[100] = 4321;

that you can use as a function parameter.

@j08691 not sure how one can loop an anonymous array. it'd be easier to define the variable upfront which is what I'm trying to avoid. — MandoMando
– MandoMando, Commented Jun 15, 2012 at 18:56

Engineer · Accepted Answer · 2012-06-15 18:59:32Z

9

Something like:

var a = new Array(100).concat([4321]);

answered Jun 15, 2012 at 18:59

Engineer

48.9k12 gold badges90 silver badges93 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

MandoMando Over a year ago

Nice. this should work for more than one entry as well: myfunction(new Array(100).concat([4321], new Array(20), [65433], new Array(999), [234], ...));

lanzz · Accepted Answer · 2012-06-15 18:57:14Z

3

Probably shortest approach (but very unreadable) would be

(a = [])[100] = 4321;

But still you can't use that directly as a function parameter, as it returns the added element, and not the entire array. You still have to call as myFunction(a).

answered Jun 15, 2012 at 18:57

lanzz

43.4k12 gold badges93 silver badges99 bronze badges

Comments

Ashley Strout · Accepted Answer · 2012-06-15 18:58:02Z

3

Pass in something like this:

myfunction({100: "foo", 101: "bar"});

This works:

function testArray(arr) {
    alert(arr[4]);
}

testArray({4: "foo"}); //alerts "foo"

answered Jun 15, 2012 at 18:58

Ashley Strout

6,2886 gold badges28 silver badges48 bronze badges

Collectives™ on Stack Overflow

how to Initialize a Javascript Array with non-zero index

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related