safeDOM

safeDOM.js

const logger = R.compose(
  R.bind(console.log, console),
  R.concat('Missing selector '),
  R.flip(R.identity)
);

const mapCb = (x) => console.log(x.textContent);

const mapper = R.map(mapCb);

const validate = R.ifElse(
  R.equals(S.Nothing()),
  logger,
  mapper
);

const queryDOM = R.compose(
  S.toMaybe, 
  R.bind(document.querySelector, document)
);

const safeQuery = R.converge(
  validate,
  queryDOM, 
  R.identity
);

safeQuery('.modal');

What are your thoughts on a little point-free style?

var warn = R.bind(console.warn, console);
var log = R.bind(console.log, console);
var queryCSS = R.bind(document.querySelector, document);
var maybeQuery = R.compose(S.toMaybe, queryCSS);
var noSelector = R.compose(S.Nothing, warn, R.concat('Missing selector: '), R.flip(R.identity));

var safeQuery = R.converge(R.ifElse(R.equals(S.Nothing()), noSelector, R.identity), maybeQuery, R.identity)

safeQuery('.container').map(log); 
// => <div class="container"></div>

safeQuery('.containers').map(log); 
// => ⚠ Missing selector: .containers, will use the above warn logger since returning Nothing

I like it. I actually started with the ifElse, but keep forgetting about R.concat. I'm going to start a repo and add you as a contributor so we can polish this thing up and publish it.

yeah probably could be cleaned up, the 1st thought was to create reusable functions where possible for example some may not need to signify to the implementors that the specific selector is missing... etc