[gnome-maps/wip/mlundblad/round-populations] utils: Add function to format population numbers

[Marcus Lundblad <mlundblad src gnome org>]

commit a83bdb0fe6f585bc7b56d488d418df701fd90391
Author: Marcus Lundblad <ml update uu se>
Date:   Sun May 16 22:52:05 2021 +0200

    utils: Add function to format population numbers
    
    Handles rounding even population numbers
    (>= 1 M and divisable by 100k) in compact
    abbreviated form (leaving out trailing zeros).

 src/utils.js       | 13 +++++++++++++
 tests/utilsTest.js |  9 +++++++++
 2 files changed, 22 insertions(+)
---
diff --git a/src/utils.js b/src/utils.js
index 64ff9dae..fe308472 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -396,6 +396,19 @@ function prettyDistance(distance, noRound) {
     }
 }
 
+/**
+ * Format a population number so that greater than or equal to a million and
+ * evenly divisiable by 100k are displayed a locale-specific compact form
+ * to handle estimated values without showing lots of zeros.
+ * Other values are formatted in full.
+ */
+function prettyPopulation(population) {
+    let notation = population >= 1000000 && population % 100000 === 0 ?
+                   'compact' : 'standard';
+
+    return population.toLocaleString(undefined, { notation: notation });
+}
+
 function uriSchemeSupported(scheme) {
     let apps = Gio.AppInfo.get_all();
     let prefix = 'x-scheme-handler/';
diff --git a/tests/utilsTest.js b/tests/utilsTest.js
index 33801860..ddd010d3 100644
--- a/tests/utilsTest.js
+++ b/tests/utilsTest.js
@@ -36,6 +36,7 @@ function main() {
     getAccuracyDescriptionTest();
     prettyTimeTest();
     prettyDistanceTest();
+    prettyPopulationTest();
     normalizeStringTest();
     validWebsiteTest();
     validEmailTest();
@@ -98,6 +99,14 @@ function prettyDistanceTest() {
     JsUnit.assertEquals('5282 ft', Utils.prettyDistance(1610, true));
 }
 
+function prettyPopulationTest() {
+    JsUnit.assertEquals('123456', Utils.prettyPopulation(123456));
+    JsUnit.assertEquals('1234567', Utils.prettyPopulation(1234567));
+    JsUnit.assertEquals('200000', Utils.prettyPopulation(200000));
+    JsUnit.assertEquals('1M', Utils.prettyPopulation(1000000));
+    JsUnit.assertEquals('2.1M', Utils.prettyPopulation(2100000));
+}
+
 function normalizeStringTest() {
     JsUnit.assertEquals('foo', Utils.normalizeString('foo'));
     JsUnit.assertEquals('fooBar', Utils.normalizeString('fooBar'));