> Simple natural language date parsing in javascript


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50Sep 8, 2019Apr 9, 2018Minified + gzip package size for @nrk/simple-date-parse in KB



Simple natural language date parsing in javascript


npm i @nrk/simple-date-parse --save
import parse from '@nrk/simple-date-parse'


  Date|Number|String, // Date to parse.
  [Number|Date]       // Relative to this date. Optional and defaults to Date.now()
) // => Date

// Examples:
parse(0|''|null) // => Date: January 1, 1970, 00:00:00 UTC
parse('foobar') // => Date: Date.now() (any invalid keywords are ignored)
parse('now') // => Date: Date.now()
parse('+ 1 second') // => 1 second in the future
parse('- 2 minutes') // => 2 minutes ago
parse('+ 1 day') // => tomorrow
parse('- 2 weeks') // => today, 2 weeks ago
parse('+ 1 month') // => today, 1 month in the future
parse('- 2 years') // => today, 2 years ago
parse('00:00 - 1 year') // => at midnight one year ago
parse('yyyy-mm-01 + 1 year') // => first day of current month next year
parse('mon + 1 days') // => Tuesday this week
parse('friday') // => Friday this week, can be in future and past
parse('friday - 1 week') // => Friday guaranteed last week
parse('friday + 1 week') // => Friday guaranteed next week
parse('2018-01-dd + 1 week') // => Current day of month, but in January 2018 plus one week
parse('yyyy-mm-01 + 1 month(s) - 1 day') // => end current month
parse('yy00-01-01 - 100 year(s)') // => 1st of January this century minus 100 years
parse('100-1-1') // => 1st of January year 100
parse('-100-1-1') // => 1st of January year -100
parse('y00', new Date(-081, 1, 1)).getFullYear() // =>  0
parse('y0y', new Date(-081, 1, 1)).getFullYear() // => -101
parse('y0', new Date(-081, 1, 1)).getFullYear() // => -80
parse('y0yy', new Date(-081, 1, 1)).getFullYear() // => -81
parse('y0', new Date(-081, 1, 1)).getFullYear() // => -180
parse('y-0-0')  // => first day of year (keeps month within year and day within month)
parse('y-4-90') // => last day of April (keeps day within month)


Why did you make simple-date-parse?

There is already a great variety of superb natural language date parsing libraries in javascript, but a great deal of them are quite forgiving and flexible in terms for formatting (for instance allowing both day before and month, understanding both "tomorrow" and "+ 1 day" etc.). Such libraries are wonderful when you are not in control of the input format, but they also comes with lots of kilobytes and needs for config for internationalisation.

simple-date-parse is more simple and strict in terms of format (allowing only +/- year|month|week|day|hour|minute|second, mon|tue|wed|tur|sat|sun and y-m-d), making parsing blazing fast and super lightweight (1.27KB gzipped). Use simple-date-parse generating interfaces like <button value="+ 1 day">Tomorrow</button> or other situations with controlled text input.

When should I not use simple-date-parse?

If you are doing date manipulation, we recommend a functional approaches provided by libraries such as Day.JS, Moment.js or date-fns. For more advanced natural language date parsing, checkout SugarJS, DateJS, Sherlock or Chrono.

Does simple-date-parse handle timezones, leap year, summertime etc.?

TL;DR: yes. Despite popular belief, the native Date object in Javascript is quite intelligent. Under the hood simple-date-parse converts operations to native function such as + 1 month === setMonth(date.getMonth() + 1). This avoid crazy calculations (such as year % 4 === leap year or new Date().getTime() + 1000 * 60 * 60 24 * 10 === 10 days from now) and lets native Date to do the heaving lifting.

Local development

First clone @nrk/simple-date-parse and install its dependencies:

git clone git@github.com:nrkno/simple-date-parse.git
cd simple-date-parse
npm install && npm test:watch

Building and committing

After having applied changes, remember to build before pushing the changes upstream.

git checkout -b feature/my-changes
# update the source code
npm run build
git commit -am "Add my changes"
git push origin feature/my-changes
# then make a PR to the master branch,
# and assign another developer to review your code

NOTE! Please also make sure to keep commits small and clean (that the commit message actually refers to the updated files).
Stylistically, make sure the commit message is Capitalized and starts with a verb in the present tense (for example Add minification support).

If you find any bugs or have a feature request, please open an issue on github!

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