JavaScript - filter()

https://www.w3schools.com/jsref/jsref_obj_array.asp

The filter() method allows you to apply a filter to an array and then return a new array based on the elements of the original that meet the condition. filter() will return whatever is in the original array whether it is a number, string, or object.

The filter() method creates an array filled with array elements that pass a test (provided as a function). filter() executes on each element of the array and does not execute the function for array elements without values. Note: filter() does not change the original array.

Example 1

const ages = [40, 11, 8, 32, 33, 16, 40];
const CheckForAdult = (age) => { return age >= 18; };

document.getElementById("demo1").innerHTML = ages.filter(CheckForAdult);

Example 2. Here's an example using a function expression. Instead of creating a separate function, were defining its definition right in the filter's argument.

const ages = [40, 11, 8, 32, 33, 16, 40];
document.getElementById("demo2").innerHTML = ages.filter((a) => a < 18 );

Example 3. Uses authors.js.

let femaleAuthors = authors.filter((author) =>
{
    if (author.gender.toLowerCase() === "female")
    {
        return author;
    }
});