meirionhughes / levelup-async-iterator

a plugin for levelup that provides a direct iterator usage via Symbol.asyncIterator

LevelUP Async Iterator

adds iterator() to levelup that returns this._db.iterator(options) plus an injected [Symbol.asyncIterator] property

Usage

this package requires that the host system support async-iteration. Currently for node 8.x, this requires running your application with:

node --harmony_async_iteration example.js

import/require levelup-async-iterator on app entry;

import 'levelup-async-iterator';
import * as levelup from 'levelup';
import * as leveldown from 'leveldown';
import * as encode from 'encoding-down';

let db = levelup(encode(leveldown('./db')));

async function main() {
  await db.put("a", "John");
  await db.put("b", "James");
  await db.put("c", "Janet");
  await db.put("d", "Joseph");

  let iter = db.iterator();  

  for await (let [key, value] of iter) {
    if(key === "a"){
      iter.it.seek("c");
    }
    console.log(key, value);
  }
}

main();

output:

D:\Code\levelup-async-iterator>ts-node example
a John
c Janet
d Joseph

iterator([options])

db.iterator() creates a iterator from the underlying store. the options parameter is the same as what you'd use for createReadStream

levelup-async-iterator's Issues

Purpose: get rid of core-js dependence

levelup-async-iterator/src/index.ts

Line 1 in eb666f4

import "core-js/modules/es7.symbol.async-iterator";

Could we use the following code to replace the core-js dependence?

// https://github.com/Microsoft/TypeScript/issues/14151#issuecomment-280812617
(<any>Symbol).asyncIterator = Symbol.asyncIterator || Symbol.for('Symbol.asyncIterator')

Use native Symbol.asyncIterator if available

• if this._db.iterator()[Symbol.asyncIterator] !== undefined)
  • don't override it and return it