iteration-typeguards

iteration-typeguards

Installation

Install with npm

npm install iteration-typeguards

Requirements

This module assumes a javascript environment implementing ES6, as it defines iterators and iterability based on the ES6 iteration protocols.

Module Contents

This module consists of two typeguard functions, isIterable and isIterator that accept any javascript value as a single argument and return a boolean for whether or not that value is a Iterable or an Iterator in the ES6 sense, respectively.

Usage with Typescript

A typescript compiler --target argument of es6 should be used. Both of the functions isIterable and isIterator are defined as typescript typeguards for the built-in iterfaces: Iterable<T> and Iterator<T>, respectively.

isIterable

import {isIterable} from "iteration-typeguards";

isIterable(5);                                  // false
isIterable<string>("oh hai");                   // true
isIterable(null);                               // false
isIterable([1,2,3]);                            // true
isIterable(new Map<any,any>([
  ["hi", 3],
  [{water: true}, "summer"]]
));                                             // true
isIterable({
  [Symbol.iterator]: function() {
              return {
                next: function() {
                  return 47;
                },
                done: false
              }
            }
});                                             // true

isIterator

import {isIterator} from "iteration-typeguards";

isIterator(5);                                  // false
isIterator<string>("oh hai");                   // false
isIterator<string>("oh hai"[Symbol.iterator]());// true
isIterator(null);                               // false
isIterator([1,2,3]);                            // false
isIterator([1,2,3][Symbol.iterator]);           // true
isIterator({
  next: function() {
    return 47;
  },
  done: false
});                                             // true

Usage without Typescript

Usage without typescript in nodejs is very similar to the typescript examples above without the type annotations. Since an ES6 environment is assumed, the import statements above should work. The more traditional nodejs require statements shown below also work.

var itGuards = require("iteration-typeguards");

itGuards.isIterable([1,2,3])                    // true
itGuards.isIterator([1,2,3][Symbol.iterator])   // true

Contributions

If you come across a case in which these typeguards do not perform as expected, please submit an issue (outlining the case) or a pull request (again, outlining the case and a possible solution).

License

MIT --- open source