bbo/es/index_by.js

bbo is a utility library of zero dependencies for javascript.

import './get_tag.js';
import isArray from './is_array.js';
import isString from './is_string.js';

/**
 * return an object from an array, keyed by the value at the given id
 */
function indexBy(arr, key) {
  if (!isArray(arr)) {
    throw new Error('expected an array for first argument');
  }

  if (!isString(key)) {
    throw new Error('expected a string for second argument');
  }

  var result = {};
  var len = arr.length;

  for (var i = 0; i < len; i++) {
    var index = arr[i] && arr[i][key];

    if (index) {
      result[index] = arr[i];
    }
  }

  return result;
}

export default indexBy;