1const arr = [1, 2, 3, 4];
2const sum = arr.reduce((a, b) => a + b, 0);
3// sum = 10

1const arr = [1,2,3,4,5]
2const sum = arr.reduce((a,b) => a+b)

1[1, 2, 3, 4].reduce((a, b) => a + b, 0)
2
3// Output: 10

1const sum = arr => arr.reduce((a, b) => a + b, 0);

1[1, 2, 3, 4].reduce((a, b) => a + b, 0)