pnpm/lib/node_modules/most/src/observable/getObservable.js

Fast, disk space efficient package manager

/** @license MIT License (c) copyright 2010-2016 original author or authors */
/** @author Brian Cavalier */
/** @author John Hann */

import symbolObservable from 'symbol-observable'

export default function getObservable (o) { // eslint-disable-line complexity
  var obs = null
  if (o) {
  // Access foreign method only once
    var method = o[symbolObservable]
    if (typeof method === 'function') {
      obs = method.call(o)
      if (!(obs && typeof obs.subscribe === 'function')) {
        throw new TypeError('invalid observable ' + obs)
      }
    }
  }

  return obs
}