Combining two arrays using conditions in Lodash

Question

Combining two arrays using conditions in Lodash

I have two different arrays as shown below:

const firstArray = [{name: "1"}, {name: "2"}, {name: "3"}, {name: "4"}, {name: "4"}];
const secondArray = [{name: "1"}, {name: "5"}, {name: "3"}, {name: "4"}, {name: "4"}, {name: "4"}, {name: "1"}, {name: "1"}, {name: "2"}];

The desired output is:

[{name: "1"}, {name: "2"}, {name: "3"}, {name: "4"}, {name: "4"}, {name: "5"}, {name: "4"}, {name: "1"}, {name: "1"}];

The resulting array should contain all elements from the first array and any unique elements from the second array that are not already present in the first array

I attempted to use _.unionBy

_.unionBy(firstArray, secondArray, 'name')

However, this only returns an array with unique 'name' values

Is there a way to achieve this using lodash?

javascript arrays lodash

Answer 1

Answer №1

If you need to combine arrays in a specific way, consider using the unionBy method from lodash library.

let mergedArray = _.unionBy(array1 , array2, 'name');

To learn more about how unionBy works, visit

Answer 2

If you need to combine arrays in a specific way, consider using the unionBy method from lodash library.

let mergedArray = _.unionBy(array1 , array2, 'name');

To learn more about how unionBy works, visit

Answer 3

Answer №2

Suppose you don't want the object `{ name: "2" }` to be the last item in the result set, you can achieve this by calculating the grouped items and then adding the desired items accordingly.

const
    array1 = [{ name: "1" }, { name: "2" }, { name: "3" }, { name: "4" }, { name: "4" }],
    array2 = [{ name: "1" }, { name: "5" }, { name: "3" }, { name: "4" }, { name: "4"}, { name: "4" }, { name: "1" }, { name: "1" }, { name: "2" }],
    counts = {},
    result = array1.map(o => (counts[o.name] = (counts[o.name] || 0) + 1, o));

result.push(...array2.filter(o => !counts[o.name] || !counts[o.name]--));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 4

Suppose you don't want the object `{ name: "2" }` to be the last item in the result set, you can achieve this by calculating the grouped items and then adding the desired items accordingly.

const
    array1 = [{ name: "1" }, { name: "2" }, { name: "3" }, { name: "4" }, { name: "4" }],
    array2 = [{ name: "1" }, { name: "5" }, { name: "3" }, { name: "4" }, { name: "4"}, { name: "4" }, { name: "1" }, { name: "1" }, { name: "2" }],
    counts = {},
    result = array1.map(o => (counts[o.name] = (counts[o.name] || 0) + 1, o));

result.push(...array2.filter(o => !counts[o.name] || !counts[o.name]--));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Combining two arrays using conditions in Lodash

Answer №1

Answer №2

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