Chapter 4 - mean with callback not works

[marcosfromrio]

JS novice to Ninja >>> node

function mean(array, callback) {
... if (callback) {
..... array.map(callback);
..... }
...
... const total = array.reduce((a, b) => a + b);
... return total / array.length;
... }
undefined
mean([8, 4, 7, 9], x => x*2);
7
mean([8, 4, 7, 9]);
7

[daz4126]

Sorry for the long delay in replying!

This is because map doesn't mutate the array. The code in the if block needs changing to:

if (callback) {
 a = array.map(callback);
 }

Hope that helps!

Daz
cc @simonmackie (to update code in ebook)