| 1 | /**
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| 2 | * This package exports a single function, {@link timeAgo},
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| 3 | * which describes the time elapsed between a given date and the current date
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| 4 | * in a human readable format (for example, `10 minutes ago`, `in 3 seconds`).
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| 5 | *
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| 6 | * @packageDocumentation
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| 7 | */
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| 8 |
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| 9 | /**
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| 10 | * `timeAgo` returns a string describing the time elapsed between
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| 11 | * a given date and the current time at which the function is called.
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| 12 | *
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| 13 | * @remarks
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| 14 | * `timeAgo` only supports the `en_US` locale.
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| 15 | *
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| 16 | * The following table describes `timeAgo`'s output.
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| 17 | *
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| 18 | * ```
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| 19 | * | Time elapsed | Past output | Future output |
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| 20 | * | --------------------- | ----------------- | ---------------- |
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| 21 | * | < 1 second | `just now` | `just now` |
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| 22 | * | < 1 minute | `N second(s) ago` | `in N second(s)` |
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| 23 | * | < 1 hour | `N minute(s) ago` | `in N minute(s)` |
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| 24 | * | < 1 day | `N hour(s) ago` | `in N hour(s)` |
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| 25 | * | < 1 month (30.5 days) | `N day(s) ago` | `in N day(s)` |
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| 26 | * | < 1 year (365 days) | `N month(s) ago` | `in N month(s)` |
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| 27 | * | > 1 year | `N year(s) ago` | `in N year(s)` |
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| 28 | * ```
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| 29 | *
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| 30 | * @example
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| 31 | * Basic usage:
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| 32 | *
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| 33 | * ```typescript
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| 34 | * import { timeAgo } from 'short-time-ago';
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| 35 | *
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| 36 | * const myDate = new Date();
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| 37 | * const description = timeAgo(myDate);
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| 38 | *
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| 39 | * // Output: `just now`.
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| 40 | * console.log(description);
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| 41 | * ```
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| 42 | *
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| 43 | * @example
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| 44 | * Specifying a custom current date with the `now` parameter:
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| 45 | *
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| 46 | * ```typescript
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| 47 | * import { timeAgo } from 'short-time-ago';
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| 48 | *
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| 49 | * const myDate = new Date('2019-01-01T00:00:00.000Z');
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| 50 | * const now = new Date('2019-01-01T00:01:00.000Z');
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| 51 | * const description = timeAgo(myDate, now);
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| 52 | *
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| 53 | * // Output: `1 minute ago`.
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| 54 | * console.log(description);
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| 55 | * ```
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| 56 | *
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| 57 | * ```typescript
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| 58 | * import { timeAgo } from 'short-time-ago';
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| 59 | *
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| 60 | * const myDate = new Date('2019-01-02T00:00:00.000Z');
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| 61 | * const now = new Date('2019-01-01T00:00:00.000Z');
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| 62 | * const description = timeAgo(myDate, now);
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| 63 | *
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| 64 | * // Output: `in 1 day`.
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| 65 | * console.log(description);
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| 66 | * ```
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| 67 | *
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| 68 | * @param date - a {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date | Date}
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| 69 | * @param now - the current date (optional, defaults to `new Date()`)
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| 70 | */
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| 71 | export function timeAgo(date: Date, now?: Date): string {
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| 72 | const units = [
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| 73 | ['year', 365 * 24 * 60 * 60 * 1000],
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| 74 | ['month', 30.5 * 24 * 60 * 60 * 1000],
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| 75 | ['day', 24 * 60 * 60 * 1000],
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| 76 | ['hour', 60 * 60 * 1000],
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| 77 | ['minute', 60 * 1000],
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| 78 | ['second', 1000],
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| 79 | ] as const;
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| 80 |
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| 81 | const diff = (now || new Date()).getTime() - date.getTime();
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| 82 | const elapsed = Math.abs(diff);
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| 83 |
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| 84 | for (const [name, size] of units) {
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| 85 | const value = Math.floor(elapsed / size);
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| 86 | if (value > 0) {
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| 87 | const plural = value > 1 ? 's' : '';
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| 88 | const description = `${value} ${name}${plural}`;
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| 89 | return diff > 0 ? `${description} ago` : `in ${description}`;
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| 90 | }
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| 91 | }
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| 92 |
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| 93 | return 'just now';
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| 94 | }
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