React trivial keys

README.md

See the discussion

Before (not good):

return <ul>{ paragraphs.map(p => <li>{ p }</li>) }</ul>;
// Each child in an array should have a unique "key" prop. Check the render method of RoomSpace. See http://fb.me/react-warning-keys for more information.

Uglier (not sure better):

return <ul>{ paragraphs.map((p, i) => <li key={ i }>{ p }</li>) }</ul>;

After (better?):

return <ul>{ keys(paragraphs, p => <li>{ p }</li>) }</ul>;

react-keys.js

'use strict';

// React-friendly map:
// returns an object indexed on array indices instead of an array
// so that React automatically uses that as keys
function keys (array, transform) {
  if (!transform) {
    transform = identity;
  }

  return array.reduce(function (object, value, index, array) {
    object["K" + index] = transform(value, index, array);
    return object;
  }, {});
}

function identity (v) {
  return v;
}

module.exports = keys;