How to Filter an Array of Objects Based on a Nested Value Array?

Filtering Array of Objects with Nested Value Arrays

Filtering an array of objects based on a nested value can be a common challenge. To address this, let's examine the provided fiddle:

Input Array:

let arrayOfElements = [
    {
        "name": "a",
        "subElements": [
            {"surname": 1},
            {"surname": 2}
        ]
    },
    {
        "name": "b",
        "subElements": [
            {"surname": 3},
            {"surname": 1}
        ]
    },
    {
        "name": "c",
        "subElements": [
            {"surname": 2},
            {"surname": 5}
        ]
    }
];

Desired Output:

let filteredArray = [
    {
        "name": "a",
        "subElements": [
            {"surname": 1}
        ]
    },
    {
        "name": "b",
        "subElements": [
            {"surname": 1}
        ]
    }
];

Original Filtering Approach:

let filteredArray = arrayOfElements.filter((element) => element.subElements.some((subElement) => subElement.surname === 1));

While this formula does filter the array, it returns objects with all surnames instead of removing them.

Improved Filtering Method:

arrayOfElements.map((element) => {
  return {...element, subElements: element.subElements.filter((subElement) => subElement.surname === 1)}
})

This method utilizes the spread operator (...) to create a new object for each element in the array. Inside the new object, the subElements property is filtered to include only those with the desired surname value (surname === 1).

Using this approach, you can filter arrays with arbitrarily deep nested objects by iteratively applying the map function to access and filter the desired data.

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