Length of a JavaScript object

Question

I have a JavaScript object. Is there a built-in or accepted best practice way to get the length of this object?

const myObject = new Object();
myObject["         


        

Answer 1

If you are using AngularJS 1.x you can do things the AngularJS way by creating a filter and using the code from any of the other examples such as the following:

// Count the elements in an object
app.filter('lengthOfObject', function() {
  return function( obj ) {
    var size = 0, key;
    for (key in obj) {
      if (obj.hasOwnProperty(key)) size++;
    }
   return size;
 }
})

Usage

In your controller:

$scope.filterResult = $filter('lengthOfObject')($scope.object)

Or in your view:

<any ng-expression="object | lengthOfObject"></any>

Answer 2

What about something like this --

function keyValuePairs() {
    this.length = 0;
    function add(key, value) { this[key] = value; this.length++; }
    function remove(key) { if (this.hasOwnProperty(key)) { delete this[key]; this.length--; }}
}

Answer 3

Here's how and don't forget to check that the property is not on the prototype chain:

var element_count = 0;
for(var e in myArray)
    if(myArray.hasOwnProperty(e))
        element_count++;

Answer 4

var myObject = new Object();
myObject["firstname"] = "Gareth";
myObject["lastname"] = "Simpson";
myObject["age"] = 21;

1. Object.values(myObject).length
2. Object.entries(myObject).length
3. Object.keys(myObject).length

Answer 5

If you know you don't have to worry about hasOwnProperty checks, you can do this very simply:

Object.keys(myArray).length

Answer 6

I'm not a JavaScript expert, but it looks like you would have to loop through the elements and count them since Object doesn't have a length method:

var element_count = 0;
for (e in myArray) {  if (myArray.hasOwnProperty(e)) element_count++; }

@palmsey: In fairness to the OP, the JavaScript documentation actually explicitly refer to using variables of type Object in this manner as "associative arrays".