using reduce to total array 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: javascript reduce sum

let nums = [1, 2, 3];

nums.reduce((curr, next) => curr + next);

Example 3: reduce javascript

//note idx and sourceArray are optional
const sum = array.reduce((accumulator, element[, idx[, sourceArray]]) => {
	//arbitrary example of why idx might be needed
	return accumulator + idx * 2 + element 
}, 0);