Counting occourences of a variable in an array filled with objects in JavaScript / Angular

Question

Lets say i have an array filled with objects like this:

 {conversation_id: 38
  id: 99
  is_seen: 1 
  message: "Hej Kristina"
  timestamp: "2015-07-08T10:50:49.000Z"'
 }

Now I wish I could find out how many of these objects has the value is_seen set to 1 and conversation_id set to 38.

I could solve this by using a forEach loop, however I am looking for a solution that is cleaner and maybe even more efficient.

My application is an AngularJs application, so I'm looking for either native JavaScript or Angular ways to solve this.

you could use Array.filter(). Something along the lines of: my_array.filter(function(el) { return el.conversation_id == 38 && is_seen == 1; }).length; — Cristian Lupascu
– Cristian Lupascu, Commented Jul 8, 2015 at 13:02

Anita · Accepted Answer · 2015-07-08 13:58:24Z

3

You can use angular js filter

  var seenObjects = $filter('filter')(itemsList, function(rule) {
     return rule.is_seen === 1 && rule.conversation_id === 38;
   });
console.log(seenObjects.length);

edited Jul 8, 2015 at 13:58

answered Jul 8, 2015 at 13:02

Anita

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1 Comment

phuzi Over a year ago

You forgot to check conversation_id.

Cristian Lupascu · Accepted Answer · 2015-07-08 13:19:40Z

2

You can use the native Array.filter() function:

var countOfSeenItems = my_array.filter(function (el) {
  return el.conversation_id == 38 && is_seen == 1; 
}).length;

edited Jul 8, 2015 at 13:19

answered Jul 8, 2015 at 13:19

Cristian Lupascu

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3 Comments

phuzi Over a year ago

Array.prototype.filter is not available in Internet Explorer before version 9 - kangax.github.io/compat-table/es5/#Array.prototype.filter

Marc Rasmussen Over a year ago

@phuzi what do you suggest for legacy then?

phuzi Over a year ago

@MarcRasmussen there's a polyfill on MDN - developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

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