ember-legacy-class-transform/.node_modules.ember-try/ember-macro-helpers/addon/normalize-array-key.js

The default blueprint for ember-cli addons.

import { isBlank } from '@ember/utils';
import {
  ARRAY_EACH,
  ARRAY_LENGTH
} from './-constants';

export default function(array, keys = []) {
  // this macro support should be extracted out
  // we should only deal with string keys in here
  if (typeof array !== 'string') {
    return array;
  }

  let props;

  let i = array.indexOf(ARRAY_EACH);
  if (i !== -1) {
    let chain = array.split('.');
    let end = chain[chain.length - 1];
    if (end.indexOf('{') === 0) {
      props = end.substring(1, end.length - 1).split(',');
    } else {
      props = [end];
    }
  } else {
    i = array.indexOf(ARRAY_LENGTH);
    props = [];
  }

  if (i === 0) {
    // empty string will be handled later by `getValue`
    // and will convert to `this`
    array = '';
  } else if (i > 0) {
    array = array.slice(0, i - 1);
  }

  keys.forEach(key => {
    // key could be a promise proxy and not resolved yet
    if (key === undefined) {
      return;
    }

    if (props.indexOf(key) === -1) {
      props.push(key);
    }
  });

  let suffix;
  if (props.length === 0) {
    suffix = ARRAY_LENGTH;
  } else {
    suffix = ARRAY_EACH;
    if (props.length === 1) {
      suffix += props[0];
    } else {
      suffix += `{${props.join(',')}}`;
    }
  }

  return isBlank(array) ? suffix : `${array}.${suffix}`;
}