simulacra/lib/feature_check.js

Data-binding function for the DOM.

'use strict'

module.exports = featureCheck

/**
 * Check if capabilities are available, or throw an error.
 *
 * @param {*} globalScope
 */
function featureCheck (globalScope, features) {
  var i, j, k, l, feature, path

  for (i = 0, j = features.length; i < j; i++) {
    path = features[i]

    if (typeof path[0] === 'string') {
      feature = globalScope

      for (k = 0, l = path.length; k < l; k++) {
        if (!(path[k] in feature)) throw new Error('Missing ' +
          path.slice(0, k + 1).join('.') + ' feature which is required.')

        feature = feature[path[k]]
      }
    }

    else {
      feature = path[0]

      for (k = 1, l = path.length; k < l; k++) {
        if (k > 1) feature = feature[path[k]]

        if (typeof feature === 'undefined') throw new Error('Missing ' +
          path[0].name + path.slice(1, k + 1).join('.') +
          ' feature which is required.')
      }
    }
  }
}