Add getWeek helper

STATUS.md

@@ -102,7 +102,7 @@
 - [x] `endOfWeek`
 - [x] `isSameWeek`
 - [x] `lastDayOfWeek`
-- [ ] `getWeek`
+- [x] `getWeek`
 - [x] `getWeekOfMonth`
 - [x] `getWeeksInMonth`
 - [ ] `setWeek`

__tests__/getWeek_test.re

@@ -0,0 +1,20 @@
+open Jest;
+
+open Js.Date;
+
+describe("getWeek", () => {
+  open ExpectJs;
+
+  test("returns the local week of year of the given date", () => {
+    let date = makeWithYMD(~year=2020., ~month=0., ~date=5., ());
+
+    date |> ReDate.getWeek |> expect |> toEqual(2.);
+  });
+
+  test("allows to specify which day is the first day of the week", () => {
+    let date = makeWithYMD(~year=2020., ~month=0., ~date=5., ());
+    let getWeek' = ReDate.getWeek(~weekStartsOn=Monday);
+
+    date |> getWeek' |> expect |> toEqual(1.);
+  });
+});

docs/week.md

@@ -184,3 +184,22 @@ let getWeeksInMonth' = ReDate.getWeeksInMonth(~weekStartsOn=Friday);
 
 date |> getWeeksInMonth';
 ```
+
+#### getWeek
+
+> Get the local week index of the given date.
+
+`let getWeek: (~weekStartsOn: day=?, Js.Date.t) => float`
+
+```reason
+let date = Js.Date.makeWithYMD(~year=2018., ~month=10., ~date=1., ());
+
+date |> ReDate.getWeek;
+```
+
+```reason
+let date = Js.Date.makeWithYMD(~year=2018., ~month=10., ~date=14., ());
+let getWeek' = ReDate.getWeek(~weekStartsOn=Monday);
+
+date |> getWeek';
+```

src/ReDate.re

@@ -610,6 +610,16 @@ let getWeeksInMonth = (~weekStartsOn=Sunday, date) => {
   );
 };
 
+let getWeek = (~weekStartsOn=Sunday, date) => {
+  let diff =
+    Js.Date.(
+      (date |> Internal.startOfWeek(~weekStartsOn) |> getTime)
+      -. (date |> Internal.startOfWeekYear(~weekStartsOn) |> getTime)
+    );
+
+  Js.Math.round(diff /. (Milliseconds.week |> float_of_int)) +. 1.;
+};
+
 /* ——[Weekday helpers]——————————— */
 
 let isSunday = Internal.is(Sunday);

src/ReDate.rei

@@ -147,6 +147,8 @@ let getWeekOfMonth: (~weekStartsOn: day=?, Js.Date.t) => float;
 
 let getWeeksInMonth: (~weekStartsOn: day=?, Js.Date.t) => int;
 
+let getWeek: (~weekStartsOn: day=?, Js.Date.t) => float;
+
 /* ——[Weekday helpers]——————————— */
 
 let isSunday: Js.Date.t => bool;