NodeJS JSON Array filtering

Question

I have used Node to retrieve a set of results from SQL and they're returned like this;

[
   {
   "event_id": 111111,
   "date_time": "2012-11-16T01:59:07.000Z",
   "agent_addr": "127.0.0.1",
   "priority": 6,
   "message": "aaaaaaaaa",
   "up_time": 9015040,
   "hostname": "bbbbbbb",
   "context": "ccccccc"
},
   {
   "event_id": 111112,
   "date_time": "2012-11-16T01:59:07.000Z",
   "agent_addr": "127.0.0.1",
   "priority": 6,
   "message": "aaaaaaaaa",
   "up_time": 9015040,
   "hostname": "bbbbbbb",
   "context": "ddddddd"
},
]

There are usually a lot of entries in the array and I need to efficiently filter the array to show only the entries that have a context of "ccccccc". I've tried a for loop, but it's incredibly slow.

Any suggesstions?

Why can't you constrain your query to only return cccccccc contexts? — Matt
– Matt, Commented Feb 4, 2013 at 10:38

khurrum qureshi · Accepted Answer · 2013-02-05 10:47:28Z

9

There is a very simple way of doing that if you want to do that in node and don't want to use sql for that you can user javascript built-in Array.filter function.

var output = arr.filter(function(x){return x.context=="ccccccc"}); //arr here is you result array

The ouput array will contains only objects having context "ccccccc".

answered Feb 5, 2013 at 10:47

khurrum qureshi

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Dharman · Accepted Answer · 2020-10-08 16:41:36Z

2

Another way of doing what Khurrum said, is with the arrow function. It has the same result but some people prefer that notation.

var output = arr.filter(x => x.context == "ccccccc" );

edited Oct 8, 2020 at 16:41

Dharman♦

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answered Oct 8, 2020 at 16:36

viga11

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Comments

Ben Evans · Accepted Answer · 2013-02-04 10:48:19Z

0

As suggested by Matt, why not include WHERE context = "ccccccc" in yout SQL query?

Else if you must keep all in maybe use one of the following to filter the results

// Place all "ccccccc" context row in an array

var ccccccc = [];

for (var i = results.length - 1; i >= 0; i--) {
  if(results[i] == 'ccccccc')
    ccccccc.push(results[i]);
};

// Place any context in an named array within an object

var contexts = {};
for (var i = results.length - 1; i >= 0; i--) {

  if(contexts[results[i]] == 'undefined')
    contexts[results[i]]

    contexts[results[i]].push(results[i]);
};

or use the underscore (or similar) filter function.

answered Feb 4, 2013 at 10:48

Ben Evans

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1 Comment

Aleksei Zabrodskii Over a year ago

There is native V8 Array.filter (I believe underscore will use that anyway).

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