donphan/app/javascript/mastodon/utils/numbers.js

72 lines
1.9 KiB
JavaScript

// @ts-check
export const DECIMAL_UNITS = Object.freeze({
ONE: 1,
TEN: 10,
HUNDRED: Math.pow(10, 2),
THOUSAND: Math.pow(10, 3),
MILLION: Math.pow(10, 6),
BILLION: Math.pow(10, 9),
TRILLION: Math.pow(10, 12),
});
const TEN_THOUSAND = DECIMAL_UNITS.THOUSAND * 10;
const TEN_MILLIONS = DECIMAL_UNITS.MILLION * 10;
/**
* @typedef {[number, number, number]} ShortNumber
* Array of: shorten number, unit of shorten number and maximum fraction digits
*/
/**
* @param {number} sourceNumber Number to convert to short number
* @returns {ShortNumber} Calculated short number
* @example
* shortNumber(5936);
* // => [5.936, 1000, 1]
*/
export function toShortNumber(sourceNumber) {
if (sourceNumber < DECIMAL_UNITS.THOUSAND) {
return [sourceNumber, DECIMAL_UNITS.ONE, 0];
} else if (sourceNumber < DECIMAL_UNITS.MILLION) {
return [
sourceNumber / DECIMAL_UNITS.THOUSAND,
DECIMAL_UNITS.THOUSAND,
sourceNumber < TEN_THOUSAND ? 1 : 0,
];
} else if (sourceNumber < DECIMAL_UNITS.BILLION) {
return [
sourceNumber / DECIMAL_UNITS.MILLION,
DECIMAL_UNITS.MILLION,
sourceNumber < TEN_MILLIONS ? 1 : 0,
];
} else if (sourceNumber < DECIMAL_UNITS.TRILLION) {
return [
sourceNumber / DECIMAL_UNITS.BILLION,
DECIMAL_UNITS.BILLION,
0,
];
}
return [sourceNumber, DECIMAL_UNITS.ONE, 0];
}
/**
* @param {number} sourceNumber Original number that is shortened
* @param {number} division The scale in which short number is displayed
* @returns {number} Number that can be used for plurals when short form used
* @example
* pluralReady(1793, DECIMAL_UNITS.THOUSAND)
* // => 1790
*/
export function pluralReady(sourceNumber, division) {
// eslint-disable-next-line eqeqeq
if (division == null || division < DECIMAL_UNITS.HUNDRED) {
return sourceNumber;
}
let closestScale = division / DECIMAL_UNITS.TEN;
return Math.trunc(sourceNumber / closestScale) * closestScale;
}