Array methods
- TypeScript course
- Beginner
- Lesson 12/89
- 4 min
Learn array methods like push, pop, and map.
Array methods
To add elements to an array use push, and to remove the last element use pop. The map method applies a function to each element and returns a new array. TypeScript checks these methods by their types.
let liste: number[] = [1, 2];
liste.push(3); // [1, 2, 3]
liste.pop(); // [1, 2]Details of push, pop and map
push appends an element to the end and returns the new length. pop removes the last element and returns it. map creates a new array, so the original array stays unchanged. Adding a wrong-typed element gives a compile error.
let isimler: string[] = ["Ali"];
isimler.push("Ayşe");
let ikili: number[] = [1, 2, 3].map(x => x * 2);
// [2, 4, 6]Practice Double the numbers
Define a number[] array named sayilar with the values [1, 2, 3]. Use map to multiply each element by two and store it in a new array called ikili. Then print the ikili array.
Starter code
// sayilar dizisini [1, 2, 3] olarak tanımla, map ile çiftle ve yazdırSample solution
let sayilar: number[] = [1, 2, 3];
let ikili: number[] = sayilar.map(x => x * 2);
console.log(ikili);Expected output
[ 2, 4, 6 ]
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does the `map` method do?
- It removes an element from the array
- It applies a function to each element and returns a new array Correct answer
- It converts the array to a string
- It mutates the array in place
Explanation: `map` applies a function to each element and returns a new array; the original array is untouched.
2 Add an element with push
let meyveler: string[] = ["elma"];
meyveler.____;let meyveler: string[] = ["elma"];
meyveler.push("armut");Explanation: `push` adds a new element to the array; `pop` is for removal and `map` for transformation.
3 Method behaviors
| Term | Meaning |
|---|---|
push |
Appends an element to the end |
pop |
Removes and returns the last element |
map |
Transforms each element and returns a new array |
x => x * 2 |
A doubling function for map |