Why is my javascript reduce function returns too much number when it comes to 0-CodePudding

With reduce function this was supposed to return 9000 but how come does it return 256000? I tested similar code before and it worked fine

function combined(...s) {
  return s.flat().reduce(x => x   x)
}

console.log(combined([1000, 1000, 1000], [1000, 1000, 1000], [1000, 1000, 1000]))

CodePudding user response：

reduce normally takes 2 parameters, in your case x holds the accumulated value, and the second parameter, y that I added, would be the current value in the iteration. You would have to use it like this:

function combined(...s){
  return s.flat().reduce((x, y) => x   y)
}

console.log(combined([1000,1000,1000],[1000,1000,1000],[1000,1000,1000]))

CodePudding user response：

Array.reduce() callback function requires 2 parameters at least: accumulator and currentValue.

Also, you can pass an initial value to the accumulator, which in this case should be 0

function combined(...s){
  return s.flat().reduce((result, x) => result   x, 0)
}

console.log(combined([1000,1000,1000],[1000,1000,1000],[1000,1000,1000]))

In your case, the x stands for the accumulator which initialized with the first element of the array: 1000, and you are basically returning accumulator accumulator, which results in the following:

- 2000 (1000   1000)
- 4000 (2000   2000)
- 8000 (4000   4000)
...
- 256000 (128000   128000)