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Code Completion 8 Challenges

Complete the JavaScript Arrays code

Practice transformations, selection, reduction, searching, non-mutating edits, materialization, and grouping with JavaScript arrays.

Intermediate ~8 min read

Challenge 1

Transform every score by doubling it.

javascript Your answer 
const result = [2, 4, 6].map(value => value * 2);

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Challenge 2

Keep only active records.

javascript Your answer 
const result = records.filter(record => record.active);

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Challenge 3

Add all prices starting from zero.

javascript Your answer 
const total = prices.reduce((sum, price) => sum + price, 0);

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Challenge 4

Find the last number greater than ten.

javascript Your answer 
const result = values.findLast(value => value > 10);

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Challenge 5

Create a new ascending numeric ordering without mutating values.

javascript Your answer 
const sorted = values.toSorted((a, b) => a - b);

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Challenge 6

Return a new array with index 1 replaced by "done".

javascript Your answer 
const next = states.with(1, "done");

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Challenge 7

Turn a Set into an array.

javascript Your answer 
const values = Array.from(new Set([1, 2, 3]));

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Challenge 8

Group products by category using an object result.

javascript Your answer 
const groups = Object.groupBy(products, product => product.category);

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