https://github.com/refractalize/zo

asynchronous query language, for the usual functional list processing functions: map, select, reduce, but async-friendly
https://github.com/refractalize/zo

Last synced: 3 months ago
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asynchronous query language, for the usual functional list processing functions: map, select, reduce, but async-friendly

• Host: GitHub
• URL: https://github.com/refractalize/zo
• Owner: refractalize
• Created: 2011-02-28T22:41:45.000Z (almost 14 years ago)
• Default Branch: master
• Last Pushed: 2011-07-15T08:20:37.000Z (over 13 years ago)
• Last Synced: 2024-09-15T17:14:09.540Z (3 months ago)
• Language: JavaScript
• Homepage:
• Size: 102 KB
• Stars: 11
• Watchers: 3
• Forks: 0
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

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README

        
# zo

What _is_ zo?

Zo is a asynchronous query language providing the usual functional programming list operators like `map`, `select` and `reduce`, but all in an async-friendly style, so they're ready to use while performing async IO operations in node.js.

# Installation

    npm install zo

# Operation

## require

    var zo = require('zo').zo;

## map

    zo([1, 2, 3])

        .map(function (item, mapTo) {

			process.nextTick(function () {

	            mapTo(item + 1);

			});

        })

        .results(function (mappedItems) {

            console.log(mappedItems);

        });

Produces: `[ 2, 3, 4 ]`

## select

    zo([1, 2, 3])

        .select(function (item, selectIf) {

			process.nextTick(function () {

            	selectIf(item > 1);

			});

        })

        .results(function (selectedItems) {

            console.log(selectedItems);

        });

Produces: `[ 2, 3 ]`

## reduce (also foldl)

    zo([1, 2, 3])

        .reduce(0, function (sum, item, reduceInto) {

			process.nextTick(function () {

            	reduceInto(sum + item);

			});

        })

        .results(function (sum) {

            console.log(sum);

        });

Produces: `6`

See also `reduceRight`, which is a synonym for `foldr`

## each

    zo([1, 2, 3])

        .each(function (item, done) {

			process.nextTick(function () {

	            console.log('item: ' + item);

	            done();

			});

        })

        .results(function (items) {

            console.log('count: ' + items.length);

        });

Produces:

    item: 1

    item: 2

    item: 3

    count: 3

## Async IO

But the whole point is when you mix it with async IO:

    var fs = require('fs');

    var zo = require('zo').zo;

    fs.readdir('.', function (err, filesAndDirectories) {

        zo(filesAndDirectories)

            .map(function (file, mapTo) {

                fs.stat(file, function (err, stat) {

                    mapTo({file: file, stat: stat});

                });

            })

            .select(function (fileAndStat, selectIf) {

                selectIf(fileAndStat.stat.isFile() && !/^\./.test(fileAndStat.file));

            })

            .map(function (fileAndStat, mapTo) {

                mapTo(fileAndStat.file + ': ' + fileAndStat.stat.size + ' bytes');

            })

            .each(function (fileWithSize, done) {

                console.log(fileWithSize);

                done();

            })

            .results(function (files) {

                console.log();

                console.log(files.length + ' files');

            });

    });