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Lesson 3 of 9 · Arrays and the Array Methods: The map, filter, reduce Pipeline

Module 7 · Arrays and the Array Methods: The map, filter, reduce Pipeline

Six Full Programs With Arrays, From a Grades Report to a Group-By

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Knowing every method is like knowing every tool in a kitchen. It does not cook dinner. This lesson cooks six dinners: six complete programs of the kind a working programmer writes in a normal week. Each one reads its input, keeps it in an array, and answers in a few readable lines.

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What is inside Six Full Programs With Arrays, From a Grades Report to a Group-By

  1. The shape every program here shares
  2. A grades report through the pipeline
  3. Word frequency with reduce
  4. A 2D grid: arrays inside an array
  5. Removing duplicates with a Set
  6. Group-by with reduce
  7. Running statistics in one reduce