JS function to resolve key path for Immutable.js

resolve_keypath.js

// @flow

import Immutable from 'immutable'

export const resolveKeyPaths = (source: Immutable.Collection, keypaths: Array<any>) => {
  const isFunction = (obj: any) => {
    return !!(obj && obj.constructor && obj.call && obj.apply);
  };

  var resolvedKeyPaths = []

  keypaths.forEach((value, index) => {
    if (isFunction(value)) {
      var subSource = source
      if (resolvedKeyPaths.length > 0) {
        subSource = source.getIn(resolvedKeyPaths)
      } 
      const indexToAdd = subSource.findIndex(value)
      if (indexToAdd > -1) resolvedKeyPaths.push(indexToAdd)
      else {
        console.error(`Cannot find index using ${value.toString()}`)
        throw `Error in ${index}th keypath`
      }
    } else {
      resolvedKeyPaths.push(value)
    }
  })

  return resolvedKeyPaths
}