shift.js

'use strict'
/*@flow*/

// Creates a function that clones dates and shifts by the
// seconds specified.
// Example:
// >>> import { seconds } from './shift'
// >>> const fiveSecondsLater = seconds(5)
// >>> const d = new Date()
// >>> fiveSecondsLater(d) - d
// 5000
export const seconds
    : (sec:number) => (date:Date) => Date
    = sec => date => {
        const shifted = new Date(date) // clone
        shifted.setSeconds(shifted.getSeconds() + sec)
        return shifted
    };

// Creates a function that clones dates and shifts them by the
// minutes specified.
// Example:
// >>> import { minutes } from './shift'
// >>> const minutesWindow = (lo, hi) => date =>
// >>>     [minutes(lo), minutes(hi)].map(f => f(date))
// >>> const within2MinWindow = minutesWindow(-1, 1)
// >>> const d = new Date('2016-07-01T18:00:00Z')
// >>> within2MinWindow(d)
// [ 2016-07-01T17:59:00.000Z, 2016-07-01T18:01:00.000Z ]
export const minutes
    : (min:number) => (date:Date) => Date
    = min =>
        seconds(min * 60)

// Creates a function that clones dates and shifts them by the
// hours specified.
// Example:
// >>> import { hours } from './shift'
// >>> const halfDaySooner = hours(-12)
// >>> const d = new Date()
// >>> halfDaySooner(d) - d
// -43200000
export const hours
    : (hr:number) => (date:Date) => Date
    = hr =>
        seconds(hr * 3600)