for-loop

Question

// input
const xs: Array<number> = [1, 2, 3]

// transformation
const double = (n: number): number => n * 2

// result: I want an array where each `xs`' element is doubled
const ys: Array<number> = []
for (let i = 0; i <= xs.length; i++) {
  ys.push(double(xs[i]))
}

Is the for loop correct?

Answer

No, it's not. The condition i <= xs.length should be i < xs.length.

As it is coded, ys's value is [ 2, 4, 6, NaN ] instead of [ 2, 4, 6 ]