Array Methods Easy Programs

#javascript #codenewbie #beginners #tutorial

1. Double Each Number
Problem:
[1, 2, 3]
Goal:
[2, 4, 6]
Solution:

let arr = [1, 2, 3];

let result = arr.map(num => num * 2);

console.log(result);

2. Get Even Numbers
Problem:
[1,2,3,4,5]
Goal:
[2,4]
Solution:

let arr = [1,2,3,4,5];

let result = arr.filter(num => num % 2 === 0);

console.log(result);

Think: “I want only some values” → use filter()

3. Sum of Numbers
Problem:
[1,2,3,4]
Goal:
10
Solution:

let arr = [1,2,3,4];

let sum = arr.reduce((acc, num) => acc + num, 0);

console.log(sum);

Think: “I want one final value” → use reduce()

4. Convert Numbers to Strings
Problem:
[1, 2, 3]
Goal:
["1", "2", "3"]
Solution:

let arr = [1,2,3];

let result = arr.map(num => num.toString());

console.log(result);

5. Find First Even Number
Problem:
[1,3,5,6,7]
Goal:
6
Solution:

let arr = [1,3,5,6,7];

let result = arr.find(num => num % 2 === 0);

console.log(result);

find() → returns first match

6. Check if All Numbers are Positive

let arr = [1,2,3];

let result = arr.every(num => num > 0);

console.log(result); // true

7. Check if Any Number is Negative

let arr = [1,2,-3];

let result = arr.some(num => num < 0);

console.log(result); // true

8. Square Only Even Numbers
Input:
[1,2,3,4]
Output:
[4,16]
Solution:

let arr = [1,2,3,4];

let result = arr
    .filter(num => num % 2 === 0)
    .map(num => num * num);

console.log(result);

Step 1: filter → Step 2: map

9. Count Numbers Greater Than 10

let arr = [5, 15, 20, 8];

let count = arr.filter(num => num > 10).length;

console.log(count); // 2

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