sum function in javascript

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

1console.log(
2  [1, 2, 3, 4].reduce((a, b) => a + b, 0)
3)
4console.log(
5  [].reduce((a, b) => a + b, 0)
6)

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

1const summation = (n) => (n * (n + 1)) / 2;

1let sum = (...para) => para.reduce((d,b) => d + b);

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