Function to warn if unexpected keys are in an object

expectKeys.js

// Shameless yak-shaving. I don't even remotely need this for
// anything right now, but wrote it due to a lament that keys
// in JavaScript {options: 'objects'} aren't checked for
// correctness and typos/misspelling can easily go unnoticed.

var _ = require('underscore');

// Expect all keys in the object to be from the list in "allowed".
// Emit a warning if they don't.
// TODO: Should compile down to nothing in production as this is
// only to debug.
function expectKeys(obj, allowed) {
  if (allowed && allowed.length >= 1) {
    var toWarnAbout = [];
    for (var k in obj) {
      if ({}.hasOwnProperty.call(obj, k) && ~allowed.indexOf(k)) {
        toWarnAbout.push(k);
      }
    }
    if (toWarnAbout.length) {
      console.warn('object has unexpected key: ' + toWarnAbout.join(', '));
      console.trace();
    }
  }
}