graphql/jsutils/safeArrayFrom.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = safeArrayFrom;

var _symbols = require("../polyfills/symbols.js");

function _typeof(obj) { "@babel/helpers - typeof"; if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof = function _typeof(obj) { return typeof obj; }; } else { _typeof = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof(obj); }

/**
 * Safer version of `Array.from` that return `null` if value isn't convertible to array.
 * Also protects against Array-like objects without items.
 *
 * @example
 *
 * safeArrayFrom([ 1, 2, 3 ]) // [1, 2, 3]
 * safeArrayFrom('ABC') // null
 * safeArrayFrom({ length: 1 }) // null
 * safeArrayFrom({ length: 1, 0: 'Alpha' }) // ['Alpha']
 * safeArrayFrom({ key: 'value' }) // null
 * safeArrayFrom(new Map()) // []
 *
 */
function safeArrayFrom(collection) {
  var mapFn = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : function (item) {
    return item;
  };

  if (collection == null || _typeof(collection) !== 'object') {
    return null;
  }

  if (Array.isArray(collection)) {
    return collection.map(mapFn);
  } // Is Iterable?


  var iteratorMethod = collection[_symbols.SYMBOL_ITERATOR];

  if (typeof iteratorMethod === 'function') {
    // $FlowFixMe[incompatible-use]
    var iterator = iteratorMethod.call(collection);
    var result = [];
    var step;

    for (var i = 0; !(step = iterator.next()).done; ++i) {
      result.push(mapFn(step.value, i));
    }

    return result;
  } // Is Array like?


  var length = collection.length;

  if (typeof length === 'number' && length >= 0 && length % 1 === 0) {
    var _result = [];

    for (var _i = 0; _i < length; ++_i) {
      if (!Object.prototype.hasOwnProperty.call(collection, _i)) {
        return null;
      }

      _result.push(mapFn(collection[String(_i)], _i));
    }

    return _result;
  }

  return null;
}