CODEWITHSUNDEEP
javascriptarraysobject
Camille
Camille

Reputation: 167

Javascript : total length of an object

I have an object like this :

MyObject { 
  Object1: ["12345", "67890"]
  Object2: ["74185"]
  Object3: ["29630", "789654"]
}

I need to get the total number of elements. In this exemple , I should get 5. I'm trying to do this in the most efficient way.

Upvotes: 1

Views: 2183

Answers (6)

Behemoth
Behemoth

Reputation: 9370

I know I'm late to the party but for completeness here is my approach using ES2019 introduced method <Array>.flat(). First you can get all arrays with Object.values() and then flat() to merge all arrays together in order to get the total length.

Since the flat()-method only flattens one layer at a time per default you can pass 2 as an argument (depth).

In terms of code length this is the most efficient way to solve your problem I've seen so far.

const myobject = {
  Object1: ["12345", "67890"],
  Object2: ["74185"],
  Object3: ["29630", "789654"],
};

console.log(Object.values(myobject).flat(2).length);

In case myobject has nested arrays you can also go with Infinity. Just to be sure ;)

const myobject = {
  Object1: [
    "1",
    "2",
    [
      ["3", "4"],
      ["5", "6"],
    ],
  ],
  Object2: ["7"],
  Object3: ["8", "9"],
};

console.log(Object.values(myobject).flat(Infinity).length);

Upvotes: 0

GibboK
GibboK

Reputation: 73998

You can consider the following code:

  • Use Object.keys() to "loop" on your object properties.
  • Use property length of each array to know how many items are in the array.
  • Increment variable count accordingly.

Please note, your MyObject was malformed because:

  • There is and assignment operator (=).
  • Missing comma (,) after each properties.
  • No use of var (I am assuming you do not want MyObject as global object).

var myObject =  {
  Object1: ["12345", "67890"],
  Object2: ["74185"],
  Object3: ["29630", "789654"]
};

var count = 0;
Object.keys(myObject).map(function(prop) {
    count+= myObject[prop].length;
});
alert(count);

Upvotes: 0

markusthoemmes
markusthoemmes

Reputation: 3120

You'll need to iterate over all keys of the map and sum the length of every array.

Functional way to do this:

function add(a, b) { return a + b; }

Object.keys(test).map(function(key) {
  return test[key].length
}).reduce(add);

Or if you're on one of the latter Node.js versions:

Object.keys(test).map(key => test[key].length).reduce((a, b) => a + b)

Upvotes: 1

Melbin T
Melbin T

Reputation: 159

Use for in loop to iterate all the objects and add the counts by find the length of the array.

While using for in its is recommended to use hasOwnProperty() to avoid unnecessory properties being iterated due to prototypical inheritance.

var count = 0;
for (var key in MyObject) {
    if (MyObject.hasOwnProperty(key)) {
        count += MyObject[key].length;
    }
}
console.log(count);

Upvotes: 0

tymeJV
tymeJV

Reputation: 104795

You can use reduce for everything!

var totalLength = Object.keys(MyObject).reduce(function(total, key) {
    return total += MyObject[key].length;
}, 0);

Upvotes: 2

James Donnelly
James Donnelly

Reputation: 128856

Use a for loop to loop through the object, checking to ensure the key is an Array before incrementing a length counter:

var count = 0;

for (var key in MyObject)
  if (MyObject[key] instanceof Array)
    count += MyObject[key].length;


var MyObject = { 
  Object1: ["12345", "67890"],
  Object2: ["74185"],
  Object3: ["29630", "789654"]
}

var count = 0;

for (var key in MyObject)
  if (MyObject[key] instanceof Array)
    count += MyObject[key].length;

console.log(count);

Upvotes: 5

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