Arrays

Array.prototype.reduce()

Signature

reduce(callbackFn, initialValue?)

Exception

TypeError: throw error if array is empty, AND initialValue is not provided

workflow

• an iterative method
• runs cbfn over all elements in the array in ascending order
• run cbfn(ans, element) => ans until element is null
• NOT invoked for empty element
• NOT support thisArg = undefined, gets substituted with globalThis if non-strict

Edge case

• default initialValue = 0

example, get Max

[1,5,2,12,124,54].reduce((ans, n) => Math.max(ans, n), 30); //124

example, get sum

[1,5,2,12,124,54].reduce((ans, n) => ans + n, 30); //124