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Generate a random date within a given range | https://jsfiddle.net/jayantbh/6x2gcnxn/2/
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// Basic Random Date Generator | |
function randomInt(a = 0, b = 0) { return (a + window.crypto.getRandomValues(new Uint8Array(1))[0] % Math.abs(b - a + 1)); } | |
function log(json) { | |
for (key in arguments) { | |
let string = JSON.stringify(arguments[key], null, ' '); | |
document.body.innerHTML += `<pre>${string}</pre> `; | |
} | |
console.log(...arguments); | |
document.body.innerHTML += '<br>'; | |
} | |
function getDaysInMonth (month, year) { | |
const isLeapYear = year % 4 === 0; | |
switch(month) { | |
case 1: case 3: case 5: case 7: case 8: case 10: case 12: return 31; break; | |
case 4: case 6: case 9: case 11: return 30; break; | |
case 2: return isLeapYear ? 29 : 28; | |
} | |
} | |
function getRandomDayInRange (start, end) { | |
if (typeof start !== 'object' || typeof end !== 'object') { throw new Error('Incorrect parameter type. `start` and `end` need to be objects with properties `day`, `month` and `year`.'); } | |
if (!start.day) { throw new Error('`start.day` needs to be defined.')} | |
if (!start.month) { throw new Error('`start.month` needs to be defined.')} | |
if (!start.year) { throw new Error('`start.year` needs to be defined.')} | |
if (!end.day) { throw new Error('`end.day` needs to be defined.')} | |
if (!end.month) { throw new Error('`end.month` needs to be defined.')} | |
if (!end.year) { throw new Error('`end.year` needs to be defined.')} | |
const year = randomInt(start.year, end.year); | |
const isStartYear = year === start.year; | |
const isEndYear = year === end.year; | |
const isStartYearButNotSameAsEndYear = isStartYear && !isEndYear; | |
const isEndYearButNotSameAsStartYear = isEndYear && !isStartYear; | |
const isNeitherStartNorEndYear = !isStartYear && !isEndYear; | |
if (isStartYearButNotSameAsEndYear) { end.month = 12; } | |
if (isEndYearButNotSameAsStartYear) { start.month = 1; } | |
if (isNeitherStartNorEndYear) { start.month = 1; end.month = 12; } | |
const month = randomInt(start.month, end.month); | |
const isStartMonth = month === start.month; | |
const isEndMonth = month === end.month; | |
const isFirstMonthButNotLast = isStartYear && isStartMonth && !isEndYear && !isEndMonth; | |
const isLastMonthButNotFirst = isEndYear && isEndMonth && !isStartYear && !isStartMonth; | |
const isNotFirstMonth = isStartYear && !isStartMonth || !isStartYear; | |
const isNotLastMonth = isEndYear && !isEndMonth || !isEndYear; | |
if (isFirstMonthButNotLast) { end.day = getDaysInMonth(month, year); } | |
if (isLastMonthButNotFirst) { start.day = 1; } | |
if (isNotFirstMonth) { start.day = 1; } | |
if (isNotLastMonth) { end.day = getDaysInMonth(month, year); } | |
if (isNeitherStartNorEndYear) { start.day = 1; end.day = getDaysInMonth(month, year); } | |
const day = randomInt(start.day, end.day); | |
return [day, month, year]; | |
} | |
function parseDate (dates) { | |
const DATE_REGEX = /\d{1,2}\-\d{1,2}\-\d{4}/; | |
if (typeof startDate !== 'string' || typeof endDate !== 'string') { throw new Error('Incorrect input type'); } | |
if (!(DATE_REGEX.test(startDate) && DATE_REGEX.test(endDate))) { throw new Error ('Incorrect date format'); } | |
let [startDay, startMonth, startYear] = startDate.split('-').map(_ => parseInt(_)); | |
let [endDay, endMonth, endYear] = endDate.split('-').map(_ => parseInt(_)); | |
return [ | |
{ day: startDay, month: startMonth, year: startYear }, | |
{ day: endDay, month: endMonth, year: endYear } | |
]; | |
} | |
// =========================================================================== | |
let [ startDate, endDate ] = ['10-06-2016', '20-06-2016']; | |
let [ start, end ] = parseDate(startDate, endDate); | |
const LIMIT = 20; | |
for (let i = 0; i < LIMIT; i++) { | |
let [day, month, year] = getRandomDayInRange(start, end); | |
log(day, month, year); | |
} | |
log('Thanks for trying this out!'); |
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