iterable.md

Iterable

Value which implements iterable protocol

iterable/is

Confirms if given object is an iterable and is not a string (unless allowString option is passed)

const isIterable = require("type/iterable/is");

isIterable([]); // true
isIterable({}); // false
isIterable("foo"); // false
isIterable("foo", { allowString: true }); // true

Supports also denyEmpty option

isIterable([], { denyEmpty: true }); // false
isIterable(["foo"], { denyEmpty: true }); // true

iterable/ensure

If given argument is an iterable, it is returned back. Otherwise TypeError is thrown. By default string primitives are rejected unless allowString option is passed.

const ensureIterable = require("type/iterable/ensure");

ensureIterable([]); // []
ensureIterable("foo", { allowString: true }); // "foo"
ensureIterable({}); // Thrown TypeError: null is not expected iterable

Denying empty iterables

Pass denyEmpty option to require non empty iterables

ensureIterable([], { denyEmpty: true }); // Thrown TypeError: [] is not expected iterable

Confirming on items

Items can be validated by passing ensureItem option. Note that in this case:

• A newly created instance of array with coerced values is returned
• Error message lists up to three invalid items

const ensureString = require("type/string/ensure");

ensureIterable(new Set(["foo", 12]), { ensureItem: ensureString }); // ["foo", "12"]

/*
 Below invocation with crash with:
 TypeError: [object Set] is not expected iterable value.
            Following items are invalid:
              - [object Object]
*/
ensureIterable(new Set(["foo", {}]), { ensureItem: ensureString });