underscore.js filter an array of objects, based on another
javascript, underscore.js
Solution
Just create a "set" of the valid ids and use that "set" to do the filtering:
var aaa = [
{name: "AAA", id: 845},
{name: "BBB", id: 839},
{name: "CCC", id: 854}
];
var bbb = [
{id: 839},
{id: 854}
];
var ids = {};
_.each(bbb, function (bb) { ids[bb.id] = true; });
var out = _.filter(aaa, function (val) {
return ids[val.id];
}, bbb);
Filling `ids` is fast, it's in n * amortized O(1), i.e O(n). Same holds for the filtering.
If you use `each(…)` in the inner loop, you will have O(n²). For bigger data sets this would become very slow. Also the additional nesting make the code more difficult to read/understand at first glance.
See that code snipped in action: http://jsfiddle.net/SMtX5/
Problem
I am trying to filter an array of objects, based on another. The common property id `id`. I am not sure filter + each is the best way to do it or map reduce. Anyway, below code doesn't work as `out` is empty list. ``` var aaa = [ {name: "AAA", id: 845}, {name: "BBB", id: 839}, {name: "CCC", id: 854} ]; var bbb = [ {id: 839}, {id: 854} ]; var out = _.filter(aaa, function(val){ return _.each(this, function(val2){ return val['id'] === val2['id'] }); }, bbb); ```