reduce javascript with string code example

Example 1: javascript sum of array

const sum = arr => arr.reduce((a, b) => a + b, 0);

Example 2: js reduce a array of straing

var authors = [{name: 'some author'},{name: 'another author'},{name: 'last author'}]
var authorString = authors.map(function(author){
    return author.name;
}).join(",");
console.log(authorString);