javascript reduce get index code example

Example 1: how to flatten array with reduce in javascript

let flattened = [[0, 1], [2, 3], [4, 5]].reduce(
  function(accumulator, currentValue) {
    return accumulator.concat(currentValue)
  },
  []
)
// flattened is [0, 1, 2, 3, 4, 5]

Example 2: .reduce mdn

arr.reduce(callback( accumulator, currentValue[, index[, array]] )[, initialValue])