Generic interface for collections in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a generic interface named Collection.

Typescript

interface Collection<[1]> {
  add(item: T): void;
  remove(item: T): void;
  size(): number;
}

Drag options to blanks, or click blank then click option'

AT

BU

CV

DK

Attempts:

3 left

💡 Hint

Common Mistakes

Using a lowercase letter for the generic type parameter.

Forgetting to put the generic parameter in angle brackets.

The generic type parameter T is commonly used to represent the type of items in the collection.

2fill in blank

medium

Complete the code to declare a class that implements the generic Collection interface.

Typescript

class List<[1]> implements Collection<T> {
  private items: T[] = [];
  add(item: T): void {
    this.items.push(item);
  }
  remove(item: T): void {
    this.items = this.items.filter(i => i !== item);
  }
  size(): number {
    return this.items.length;
  }
}

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AK

BV

CT

DU

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different generic parameter than the interface.

Not declaring the generic parameter on the class.

The class uses the same generic type parameter T as the interface it implements.

3fill in blank

hard

Fix the error in the method signature to correctly use the generic type parameter.

Typescript

remove(item: [1]): void {
  this.items = this.items.filter(i => i !== item);
}

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Aany

BT

Cunknown

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-generic type like any or object.

Forgetting to use the generic type parameter.

The method parameter must use the generic type T to match the collection item type.

4fill in blank

hard

Fill both blanks to create a generic function that returns the first item of a collection.

Typescript

function getFirst<[1]>(collection: Collection<T>): [2] | undefined {
  // Assume collection has a method to get all items as array
  const items = (collection as any).items as T[];
  return items[0];
}

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AT

BU

DV

Attempts:

3 left

💡 Hint

Common Mistakes

Using different generic parameters in declaration and return type.

Not declaring the generic parameter in the function.

The generic type parameter T is used both to declare the function and as the return type.

5fill in blank

hard

Fill all three blanks to define a generic interface with a method that returns an array of items.

Typescript

interface Collection<[1]> {
  add(item: T): void;
  getAll(): [2][];
  size(): [3];
}

Drag options to blanks, or click blank then click option'

AT

Bnumber

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using string instead of number for size.

Not using the generic type for the array return type.

The generic type T is used for the item type and array return type, while number is the return type for size().