github-pages-deploy-action/node_modules/graphql/jsutils/isCollection.js.flow
2020-03-06 22:45:40 -05:00

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// @flow strict
import { SYMBOL_ITERATOR } from '../polyfills/symbols';
/**
* Returns true if the provided object is an Object (i.e. not a string literal)
* and is either Iterable or Array-like.
*
* This may be used in place of [Array.isArray()][isArray] to determine if an
* object should be iterated-over. It always excludes string literals and
* includes Arrays (regardless of if it is Iterable). It also includes other
* Array-like objects such as NodeList, TypedArray, and Buffer.
*
* @example
*
* isCollection([ 1, 2, 3 ]) // true
* isCollection('ABC') // false
* isCollection({ length: 1, 0: 'Alpha' }) // true
* isCollection({ key: 'value' }) // false
* isCollection(new Map()) // true
*
* @param obj
* An Object value which might implement the Iterable or Array-like protocols.
* @return {boolean} true if Iterable or Array-like Object.
*/
export default function isCollection(obj: mixed): boolean {
if (obj == null || typeof obj !== 'object') {
return false;
}
// Is Array like?
const length = obj.length;
if (typeof length === 'number' && length >= 0 && length % 1 === 0) {
return true;
}
// Is Iterable?
return typeof obj[SYMBOL_ITERATOR] === 'function';
}