How to use jQuery.map() on array of objects to return array of arrays

Question

I would like to use jQuery to convert an array of objects to array of arrays using map.

For example if I have this:

var ObjArr = [{ a:1,b:2 },{ a:2,b:3 },{ a:3,b:4 }];
var ArrArr = $.map(ObjArr, function(n,i){
   return [ n.a, n.b ];
});

So that the result would be:

ArrArr = [[1,2],[2,3],[3,4]]

user113716 · Accepted Answer · 2011-02-02 14:35:09Z

96

With the jQuery.map()^(docs) and map()^(docs) methods you need to double wrap the return value:

var ArrArr = $.map(ObjArr, function(n,i){
   return [[ n.a, n.b ]];
});

...otherwise for some reason it concats the Array being returned. This way it concats the outer Array, and placing the content (the inner Array) at the next index.

answered Feb 2, 2011 at 14:35

user113716

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2 Comments

iplus26 Over a year ago

It works! However, could you tell me is there any reason why jQuery does it?

antak Over a year ago

could you tell me is there any reason why jQuery does it: Probably to make .map() not restricted to a 1:1 mapping. e.g. Returning [] can filter out the element without using a separate .filter(). Likewise .map() can also be used to flatten a list of lists.

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