use fixed locale for formatting numbers in JS and Wasm, and add some KDoc for explanation

Author: adam-enko

runtime/commonMain/src/kotlinx/benchmark/ReportBenchmarksStatistics.kt

@@ -86,6 +86,13 @@ class ReportBenchmarksStatistics(values: DoubleArray) {
     }
 }
 
+/**
+ * Pretty formats a number.
+ *
+ * The locale must be fixed, so that decimals will be consistently formatted.
+ * - `.` - decimal separator
+ * - `,` - thousands separator
+ */
 internal expect fun Double.format(precision: Int, useGrouping: Boolean = true): String
 
 fun Double.formatSignificant(precision: Int): String {
@@ -126,7 +133,7 @@ fun Double.sampleToText(mode: Mode, unit: BenchmarkTimeUnit): String {
 
 @Suppress("REDUNDANT_ELSE_IN_WHEN")
 fun Double.nanosToSample(mode: Mode, unit: BenchmarkTimeUnit): Double {
-    val multiplier = unit.toMultiplier() // unit in nanos 
+    val multiplier = unit.toMultiplier() // unit in nanos
     return when (mode) {
         Mode.Throughput -> multiplier / this
         Mode.AverageTime -> this / multiplier

runtime/jsMain/src/kotlinx/benchmark/UtilsJs.kt

@@ -5,7 +5,7 @@ internal actual fun Double.format(precision: Int, useGrouping: Boolean): String
     options.minimumFractionDigits = precision
     options.maximumFractionDigits = precision
     options.useGrouping = useGrouping
-    return this.asDynamic().toLocaleString(undefined, options) as String
+    return this.asDynamic().toLocaleString("en-GB", options) as String
 }
 
 internal actual fun String.writeFile(text: String): Unit = jsEngineSupport.writeFile(this, text)

runtime/wasmJsMain/src/kotlinx/benchmark/Utils.kt

@@ -1,6 +1,6 @@
 package kotlinx.benchmark
 
-@JsFun("(d, precision, useGrouping) => d.toLocaleString(undefined, { maximumFractionDigits: precision, minimumFractionDigits: precision, useGrouping: useGrouping } )")
+@JsFun("(d, precision, useGrouping) => d.toLocaleString('en-GB', { maximumFractionDigits: precision, minimumFractionDigits: precision, useGrouping: useGrouping } )")
 private external fun format(d: Double, precision: Int, useGrouping: Boolean): String
 
 internal actual fun Double.format(precision: Int, useGrouping: Boolean): String = format(this, precision, useGrouping)
@@ -31,4 +31,4 @@ internal val jsEngineSupport: JsEngineSupport by lazy {
 internal external interface ExternalInterfaceType
 
 internal actual inline fun measureNanoseconds(block: () -> Unit): Long =
-    if (isD8) d8MeasureTime(block) else nodeJsMeasureTime(block)
+    if (isD8) d8MeasureTime(block) else nodeJsMeasureTime(block)