array chaining

things.js

let things = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

let other = things
  .map(function(num) { return num + 1; }) // creates a new array that contains [2, 3, 4, 5, 6, 7, 8, 9, 10, 11] and returns it
  .filter(function(num) { return num % 3 === 0; }) // reduces the array contents so that it contains [3, 6, 9] and returns it
  .join(' -> '); // joins the values and returns a string '3 -> 6 -> 9'

// This could just as easily be written as follows

let a = things.map(function(num) { return num + 1; });
let b = a.filter(function(num) { return num % 3 === 0; });
let c = b.join(' -> ');

// But this means that we have extra variables laying around that we may not use.  If you write
// them as simple chained manipulations we know that the intermediate values are not important and ar thrown away.