How to use hasOwnProperty & for…in loop In Javascript
- By using for…in loop we can iterate over the object.
- By checking obj.hasOwnProperty(key), we check it contains only own properties (not inherited) are counted.
- Increment the size variable for each own property found, which represents the length of the associative array.
Example: Below is the implementation of the above approach
// Function to calculate the
// length of an array
sizeOfArray = function (array) {
// A variable to store
// the size of arrays
let size = 0;
// Traversing the array
for (let key in array) {
// Checking if key is present
// in arrays or not
if (array.hasOwnProperty(key)) {
size++;
}
}
// Return the size
return size;
}
// Driver code
let arr = { "apple": 10, "grapes": 20 };
arr["guava"] = 30;
arr["banana"] = 40;
// Printing the array
console.log(arr);
// Printing the size
console.log("size = " + sizeOfArray(arr));
// Adding another element to array
arr["fruits"] = 100;
// Printing the array and size again
console.log(arr);
console.log("Size = " + sizeOfArray(arr));
Output
{ apple: 10, grapes: 20, guava: 30, banana: 40 } size = 4 { apple: 10, grapes: 20, guava: 30, banana: 40, fruits: 100 } Size = 5
Calculate the length of an associative array using JavaScript
In JavaScript, we have normal arrays in which an element is present at a particular index. Whereas Associative arrays are basically Objects in JavaScript where the index is replaced with user-defined keys. Basically, we can say that it stores Key-Value pairs.
Syntax:
let arr = { key1: 'value'1, key2: 'value2', key3: 'value3'}
Here, arr is the associative array, key1, key2, and key3 are its indexes, and value1, value2, and value3 are its elements.
Example: This is a basic example of the associative property.
let arr = {
"apple": 10,
"grapes": 20
};
arr["guava"] = 30;
arr["banana"] = 40;
console.log("Apple = " + arr.apple)
console.log("Banana = " + arr.banana)
Output
Apple = 10 Banana = 40
Length of an associative array: Like in a normal array, an associative array does not have a length property. So we will see other ways to calculate the length of associative arrays.
To calculate the length of an associative array, we will traverse the array element and count all the keys present in the array.
We can calculate the length of an associative array in the following ways:
Table of Content
- Using hasOwnProperty & for…in loop
- Using the keys Method
- Using Object.entries() Method
- Using Object.getOwnPropertyNames() and length property
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