| const IO = f => ({ | |
| runIO: f, | |
| map: g => | |
| IO(() => g(f())), | |
| chain: g => | |
| IO(g(f()).runIO) | |
| }) | |
| const log = label => x => | |
| IO(() => (console.log(label, x), x)) | |
| const $ = x => | |
| IO(() => document.querySelector(x)) | |
| const getText = e => | |
| e.textContent | |
| const main = selector => | |
| $(selector) | |
| .map(getText) | |
| .chain(log('A')) | |
| .map(s => s.toUpperCase()) | |
| .chain(log('B')) | |
| .runIO() | |
| main('title') | |
| // A hello world | |
| // B HELLO WORLD |