I've written a method to calculate the number of objects in an array which have 'enabled' set to 'true'.

I'm adding 1 to counter each time it finds an object in my array which has 'enabled' set to 'true'.

How could I achieve this without using 'counter' variable and using reduce or filter instead??

Here's my code:

function getCount() {               
    const arr =[[{ "enabled": true }], [{ "enabled": false}, {"enabled": true}]];                       
    var count = 0;
    arr.forEach(function(ar){
        ar.forEach(function(obj){
            if(obj.enabled) {
                count++;
            }
        })
    });
    return count;           
}

I've written a method to calculate the number of objects in an array which have 'enabled' set to 'true'.

I'm adding 1 to counter each time it finds an object in my array which has 'enabled' set to 'true'.

How could I achieve this without using 'counter' variable and using reduce or filter instead??

Here's my code:

function getCount() {               
    const arr =[[{ "enabled": true }], [{ "enabled": false}, {"enabled": true}]];                       
    var count = 0;
    arr.forEach(function(ar){
        ar.forEach(function(obj){
            if(obj.enabled) {
                count++;
            }
        })
    });
    return count;           
}

• javascript
• multidimensional-array
• filter
• ecmascript-6
• reduce

• What is obj.seatMapAvailable? Did you mean obj.enabled? – StudioTime Commented Oct 31, 2018 at 13:00
• yes, that's true, corrected it now! I want to use reduce from ES6. – Sunny Commented Oct 31, 2018 at 13:10

4 Answers 4

Have a look below, I've added a comment:

[].concat(...arr) /* flatten the array */
.filter(item => item.enabled) /* return only enabled: true */
.length /* get the count */

const arr = [
  [{
    "enabled": true
  }],
  [{
    "enabled": false
  }, {
    "enabled": true
  }]
];
var enabledCount = [].concat(...arr).filter(item => item.enabled).length
console.log(enabledCount)

Or you can use reduce, if you want

const arr = [
  [{
    "enabled": true
  }],
  [{
    "enabled": false
  }, {
    "enabled": true
  }]
];

var enabledCount = arr.reduce(
  (accumulator, currentValue) => accumulator.concat(currentValue), []
).filter(item => item.enabled).length

console.log(enabledCount)

Using a helper reduce function gives the simplest implementation in my opinion:

const arr =[
 [
     {"enabled": true},
     {"enabled": true}
 ],
 [
     {"enabled": false}, 
     {"enabled": true},
     {"enabled": true}
 ]
]; 

// Helper function to count inner arrays
const r = (i) => i.reduce( (p, c) => c.enabled ? p = p + 1 : p, 0)

const count = arr.reduce( (p, c) => p + r(c), 0) // Output: 4

Would something like this work?

const arr =[[{ "enabled": true }], [{ "enabled": false}, {"enabled": true}]];               
const enabledArray = arr.map(function(item) {
    return item.filter(function(subItem){
        return subItem.enabled === true;
    })
})
const enabledItems = enabledArray.length;

You could do:

const arr = [[{ "enabled": true }], [{ "enabled": false }, { "enabled": true }]];

console.log(
    arr.reduce(
    // Flatten the array of arrays
        (acc, curVal) => acc.concat(curVal), []         
    ).filter(
    // Filter so you have an array with 
    //       objects that have 'enable': true
        (obj) => Object.is(obj['enabled'], true))
    // and then return the length of it
    .length
);