Rounding options to toRelative

src/datetime.js

@@ -447,8 +447,9 @@ function quickDT(obj, opts) {
 
 function diffRelative(start, end, opts) {
   const round = isUndefined(opts.round) ? true : opts.round,
+    rounding = isUndefined(opts.rounding) ? "trunc" : opts.rounding,
     format = (c, unit) => {
-      c = roundTo(c, round || opts.calendary ? 0 : 2, true);
+      c = roundTo(c, round || opts.calendary ? 0 : 2, opts.calendary ? "round" : rounding);
       const formatter = end.loc.clone(opts).relFormatter(opts);
       return formatter.format(c, unit);
     },
@@ -2193,12 +2194,13 @@ export default class DateTime {
 
   /**
    * Returns a string representation of a this time relative to now, such as "in two days". Can only internationalize if your
-   * platform supports Intl.RelativeTimeFormat. Rounds down by default.
+   * platform supports Intl.RelativeTimeFormat. Rounds towards zero by default.
    * @param {Object} options - options that affect the output
    * @param {DateTime} [options.base=DateTime.now()] - the DateTime to use as the basis to which this time is compared. Defaults to now.
    * @param {string} [options.style="long"] - the style of units, must be "long", "short", or "narrow"
    * @param {string|string[]} options.unit - use a specific unit or array of units; if omitted, or an array, the method will pick the best unit. Use an array or one of "years", "quarters", "months", "weeks", "days", "hours", "minutes", or "seconds"
    * @param {boolean} [options.round=true] - whether to round the numbers in the output.
+   * @param {string} [options.rounding="trunc"] - rounding method to use when rounding the numbers in the output. Can be "trunc" (toward zero), "expand" (away from zero), "round", "floor", or "ceil".
    * @param {number} [options.padding=0] - padding in milliseconds. This allows you to round up the result if it fits inside the threshold. Don't use in combination with {round: false} because the decimal output will include the padding.
    * @param {string} options.locale - override the locale of this DateTime
    * @param {string} options.numberingSystem - override the numberingSystem of this DateTime. The Intl system may choose not to honor this

src/impl/util.js

@@ -159,10 +159,24 @@ export function parseMillis(fraction) {
   }
 }
 
-export function roundTo(number, digits, towardZero = false) {
-  const factor = 10 ** digits,
-    rounder = towardZero ? Math.trunc : Math.round;
-  return rounder(number * factor) / factor;
+export function roundTo(number, digits, rounding = "round") {
+  const factor = 10 ** digits;
+  switch (rounding) {
+    case "expand":
+      return number > 0
+        ? Math.ceil(number * factor) / factor
+        : Math.floor(number * factor) / factor;
+    case "trunc":
+      return Math.trunc(number * factor) / factor;
+    case "round":
+      return Math.round(number * factor) / factor;
+    case "floor":
+      return Math.floor(number * factor) / factor;
+    case "ceil":
+      return Math.ceil(number * factor) / factor;
+    default:
+      throw new RangeError(`Value rounding ${rounding} is out of range`);
+  }
 }
 
 // DATE BASICS

test/datetime/relative.test.js

@@ -43,6 +43,144 @@ test("DateTime#toRelative takes a round argument", () => {
   expect(base.minus({ months: 15 }).toRelative({ base, round: false })).toBe("1.25 years ago");
 });
 
+test("DateTime#toRelative takes a rounding argument", () => {
+  const base = DateTime.fromObject({ year: 1983, month: 10, day: 14 });
+  expect(base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "expand" })).toBe(
+    "in 2 hours"
+  );
+  expect(base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "expand" })).toBe(
+    "in 3 hours"
+  );
+  expect(base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "expand" })).toBe(
+    "2 hours ago"
+  );
+  expect(base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "expand" })).toBe(
+    "3 hours ago"
+  );
+
+  expect(base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "trunc" })).toBe(
+    "in 1 hour"
+  );
+  expect(base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "trunc" })).toBe(
+    "in 2 hours"
+  );
+  expect(base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "trunc" })).toBe(
+    "1 hour ago"
+  );
+  expect(base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "trunc" })).toBe(
+    "2 hours ago"
+  );
+
+  expect(base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "round" })).toBe(
+    "in 2 hours"
+  );
+  expect(base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "round" })).toBe(
+    "in 2 hours"
+  );
+  expect(base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "round" })).toBe(
+    "2 hours ago"
+  );
+  expect(base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "round" })).toBe(
+    "2 hours ago"
+  );
+
+  expect(base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "floor" })).toBe(
+    "in 1 hour"
+  );
+  expect(base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "floor" })).toBe(
+    "in 2 hours"
+  );
+  expect(base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "floor" })).toBe(
+    "2 hours ago"
+  );
+  expect(base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "floor" })).toBe(
+    "3 hours ago"
+  );
+
+  expect(base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "ceil" })).toBe(
+    "in 2 hours"
+  );
+  expect(base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "ceil" })).toBe(
+    "in 3 hours"
+  );
+  expect(base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, rounding: "ceil" })).toBe(
+    "1 hour ago"
+  );
+  expect(base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, rounding: "ceil" })).toBe(
+    "2 hours ago"
+  );
+});
+
+test("DateTime#toRelative takes a round and a rounding argument", () => {
+  const base = DateTime.fromObject({ year: 1983, month: 10, day: 14 });
+  expect(
+    base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "expand" })
+  ).toBe("in 2 hours");
+  expect(
+    base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "expand" })
+  ).toBe("in 2.01 hours");
+  expect(
+    base
+      .minus({ hours: 2, milliseconds: -1 })
+      .toRelative({ base, round: false, rounding: "expand" })
+  ).toBe("2 hours ago");
+  expect(
+    base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "expand" })
+  ).toBe("2.01 hours ago");
+
+  expect(
+    base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "trunc" })
+  ).toBe("in 1.99 hours");
+  expect(
+    base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "trunc" })
+  ).toBe("in 2 hours");
+  expect(
+    base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "trunc" })
+  ).toBe("1.99 hours ago");
+  expect(
+    base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "trunc" })
+  ).toBe("2 hours ago");
+
+  expect(
+    base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "round" })
+  ).toBe("in 2 hours");
+  expect(
+    base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "round" })
+  ).toBe("in 2 hours");
+  expect(
+    base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "round" })
+  ).toBe("2 hours ago");
+  expect(
+    base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "round" })
+  ).toBe("2 hours ago");
+
+  expect(
+    base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "floor" })
+  ).toBe("in 1.99 hours");
+  expect(
+    base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "floor" })
+  ).toBe("in 2 hours");
+  expect(
+    base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "floor" })
+  ).toBe("2 hours ago");
+  expect(
+    base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "floor" })
+  ).toBe("2.01 hours ago");
+
+  expect(
+    base.plus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "ceil" })
+  ).toBe("in 2 hours");
+  expect(
+    base.plus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "ceil" })
+  ).toBe("in 2.01 hours");
+  expect(
+    base.minus({ hours: 2, milliseconds: -1 }).toRelative({ base, round: false, rounding: "ceil" })
+  ).toBe("1.99 hours ago");
+  expect(
+    base.minus({ hours: 2, milliseconds: 1 }).toRelative({ base, round: false, rounding: "ceil" })
+  ).toBe("2 hours ago");
+});
+
 test("DateTime#toRelative takes a unit argument", () => {
   const base = DateTime.fromObject({ year: 2018, month: 10, day: 14 }, { zone: "UTC" });
   expect(base.plus({ months: 15 }).toRelative({ base, unit: "months" })).toBe("in 15 months");