Filter Array of objects and count the filtered elements in Javascript

Question

I have array of different objects which look like this:

[{
   color:'red',
   'type':'2',
   'status':'true'
 }
 {
   color:'red',
   'type':'2',
   'status':'false'
 }]

I want to filter the one element like status and then count the filtered, for example if status is false then return 1.

I have tried the below code but I am not sure what I am doing here:

for (i = 0; i < check.length; i++) {
  var check2;

  console.log(check[i].isApproved);
  (function(check2) {
    return check2 = check.filter(function(val) { 
        return val == false 
    }).length;
  })(check2)

  console.log('again Rides',check2);
}

Further explanation is required. The word 'filtered' is being used too liberally. This is very unclear... — IronAces
– IronAces, Commented Nov 2, 2016 at 15:15

taguenizy · Accepted Answer · 2016-11-02 15:17:38Z

28

If I understood correctly you want to count the number of elements where status is equal to 'false' note: The values you have in status are strings

var check = [
  { color:'red', 'type':'2', 'status':'true' }, 
  { color:'red', 'type':'2', 'status':'false' } 
];

var countfiltered = check.filter(function(element){
    return element.status == 'false';
}).length

console.log(countfiltered);

answered Nov 2, 2016 at 15:17

taguenizy

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1 Comment

jarmod Over a year ago

Updated with newer JS features: const countfiltered = check.filter((c) => c.status === "false").length;

TOPKAT · Accepted Answer · 2023-01-06 15:06:19Z

Given this dataset:

const items = [
  { color:'red', type:'2', status:'true' }, 
  { color:'red', type:'2', status:'false' } 
];

Here are two way to solve the problem:

Using reduce

const falseNb = items.reduce((n, item) => item.status === 'false' ? n+1 : n, 0)

Using filter

const falseNb = items.filter(e => e.status === 'false').length;

Please note that according to this test, the reduce method is twice more performant

const items = [
  { color:'red', type:'2', status:'true' }, 
  { color:'red', type:'2', status:'false' } ,
  { color:'red', type:'2', status:'false' } ,
  { color:'green', type:'1', status:'false' } ,
  { color:'red', type:'1', status:'true' } 
]

const falseNb = items.reduce((n, e) => e.status === 'false' ? n+1 : n, 0)

document.getElementById('result1').innerHTML = falseNb

const falseNbFilter = items.filter(e => e.status === 'false').length

document.getElementById('result2').innerHTML = falseNb

body { background: #333; color: #0f0; font-family: monospace}

<pre>
[
  { color:'red', type:'2', status:'true' }, 
  { color:'red', type:'2', status:'false' } ,
  { color:'red', type:'2', status:'false' } ,
  { color:'green', type:'1', status:'false' } ,
  { color:'red', type:'1', status:'true' } 
]
</pre>
Result with Reduce => <span id='result1'></span><br><br>

Result with Filter => <span id='result2'></span>

Tim Consolazio · Accepted Answer · 2016-11-02 15:23:24Z

Well, you could just do a count, or you could run a filter and get the length of the final array.

var count = 0;
var arr = [{color:'red', type:'2', status:'true'},
           {color:'red', type:'2', status:'false'} ];
// Showing filterin to be robust. You could just do this in 
// a loop, which would be sensible if you didn't need the subarray. 
var filtered = arr.filter ( function ( d ) {
    // Note that I'm testing for a string, not a boolean, because
    // you are using strings as values in your objects. 
    // If it was a boolean, you'd use if ( d.status ) { ... }
    count++;
    return d.status === 'false';
});

// These should be the same, reflecting number of objs with 'false'
console.log ( count );
console.log ( filtered.length );
// This should trace out a sub array of objs with status === 'false'
console.log ( filtered );

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Filter Array of objects and count the filtered elements in Javascript

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