bbo/index_by.js

bbo is a utility library of zero dependencies for javascript.

'use strict';

require('./get_tag.js');
var is_array = require('./is_array.js');
var is_string = require('./is_string.js');

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

  if (!is_string(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;
}

module.exports = indexBy;