javascript getting an array from an array in an object

Question

I have an object MyObject and one of its properties ItemIDs is an array of ints. I want to get a new array PageItemIDs that contains only part of the ints. It's for a pager; I pass in the page number PageNumber and I get the IDs of the items on the page. Suppose the page size is 20 items.

This is what I tried. It doesn't work because js works with references so I end up changing the array of the object.

PageItemIDs = MyObject.ItemsID;
PageItemIDs = PageItemIDs.splice(PageNumber * 20, 20);

And instead of getting the ItemIDs in the page, I end up with the ItemIDs not in the page.

I know I'm not that far off but if you can help that'd be nice.

Thanks.

Edit:

When I do

PageItemIDs = PageItemIDs.slice((PageNumber -1) * 20, 20);

it works for page 1 but for every other page, it returns an empty array.

Ok, I got it, nevermind.

 PageItemIDs = PageItemIDs.slice(PageNumber * 20, PageNumber * 20);

rid · Accepted Answer · 2012-05-17 22:13:22Z

1

Use slice() instead of splice().

slice() returns a slice of the array, splice() changes the contents of the array in-place.

answered May 17, 2012 at 22:13

rid

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5 Comments

frenchie Over a year ago

ok, slice keeps the original array intact. However PageItemIDs.splice(PageNumber * 20, 20); with PageNumber = 1 returns the same array with all the elements, instead of page 1.

rid Over a year ago

@frenchie, slice() works differently than splice(). slice() takes the begin and end of the portion you want to slice. splice() takes an index and a count.

frenchie Over a year ago

PageItemIDs = PageItemIDs.slice(1 * 20, 20); returns array 0 elements.

rid Over a year ago

@frenchie, of course, because you're asking for all elements between 20 and 20. If you want all elements between 20 and 40, use slice(1 * 20, 40) instead.

frenchie Over a year ago

ok, I got it: PageItemIDs = PageItemIDs.splice(PageNumber * 20, PageNumber * 20); Yes, I meant slice!

Sebas · Accepted Answer · 2012-05-17 23:02:16Z

1

PageItemIDs = cloneObject(MyObject).ItemsID;
PageItemIDs = PageItemIDs.splice(PageNumber * 20, 20);

edited May 17, 2012 at 23:02

answered May 17, 2012 at 22:13

Sebas

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5 Comments

frenchie Over a year ago

Object #<Object> has no method 'cloneNode'

Sebas Over a year ago

could you post how MyObject is defined please?

frenchie Over a year ago

It's defined as an array of ints.

Sebas Over a year ago

Thank you, this is really kind of you ;)

Sebas Over a year ago

what the ... THANKS! That's what is happening when you don't double check your code! There is a tipo + functional mistake here, correcting it right now!!

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