How to add elements to the end of an array using JavaScript and deduplicate them, and then return the specified number of elements in reverse order?

This article introduces a JavaScript function that implements the function of adding elements to the end of an array, removing duplicate elements, and returning a specified number of elements in reverse order.

Here are some test cases:

 // Test Case 1
let list1 = [
    { id: 2 },
    { id: 3 },
    { id: 4 }
];
let newelement1 = { id: 2 };
console.log(updateList(list1, newelement1)); // Expected output: [{id: 2}, {id: 3}, {id: 4}]

// Test Case 2
let list2 = [
    { id: 1 },
    { id: 2 },
    { id: 3 },
    { id: 4 }
];
let newelement2 = { id: 3 };
console.log(updateList(list2, newelement2)); // Expected output: [{id: 3}, {id: 2}, {id: 1}]

// Test Case 3
let list3 = [
    { id: 1 },
    { id: 2 },
    { id: 3 },
    { id: 4 }
];
let newelement3 = { id: 5 };
console.log(updateList(list3, newelement3)); // Expected output: [{id: 5}, {id: 4}, {id: 3}]

The implementation code is as follows:

 function updateList(list, newElement) {
    // Process non-array input if (!Array.isArray(list)) {
        list = [];
    }

    // Object comparison function const isEqual = (a, b) => JSON.stringify(a) === JSON.stringify(b);

    // Find and remove duplicate elements list = list.filter(item => !isEqual(item, newElement));

    // Add new element list.push(newElement);

    // Return the three elements in reverse order: list.slice(-3).reverse();
}

The function first checks whether the input is an array, and if not, it is initialized to an empty array. Then use JSON.stringify for object comparison, find and remove the same element as the new element. Then add the new element to the end of the array, and finally intercept the three elements of the array and return in reverse order. This method is more efficient and concise than using Object.keys and every method. This function ensures that the input is empty or non-arrays runs normally and handles the issue of object comparison, making it more robust.

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