JS stdlib: implement String.compareTo with ignoreCase

#KT-18067 Fixed

libraries/stdlib/common/src/kotlin/TextH.kt

@@ -290,6 +290,11 @@ expect fun Int.toString(radix: Int): String
 @SinceKotlin("1.2")
 expect fun Long.toString(radix: Int): String
 
+/**
+ * Compares two strings lexicographically, optionally ignoring case differences.
+ */
+expect fun String.compareTo(other: String, ignoreCase: Boolean = false): Int
+
 @PublishedApi
 internal expect fun checkRadix(radix: Int): Int
 

libraries/stdlib/js/src/kotlin/string.kt

@@ -73,3 +73,34 @@ public inline val CharSequence.size: Int get() = length
 
 @kotlin.internal.InlineOnly
 internal inline fun String.nativeReplace(pattern: RegExp, replacement: String): String = asDynamic().replace(pattern, replacement)
+
+public actual fun String.compareTo(other: String, ignoreCase: Boolean): Int {
+    if (ignoreCase) {
+        val n1 = this.length
+        val n2 = other.length
+        val min = minOf(n1, n2)
+        if (min == 0) return n1 - n2
+        var start = 0
+        while (true) {
+            val end = minOf(start + 16, min)
+            var s1 = this.substring(start, end)
+            var s2 = other.substring(start, end)
+            if (s1 != s2) {
+                s1 = s1.toUpperCase()
+                s2 = s2.toUpperCase()
+                if (s1 != s2) {
+                    s1 = s1.toLowerCase()
+                    s2 = s2.toLowerCase()
+                    if (s1 != s2) {
+                        return s1.compareTo(s2)
+                    }
+                }
+            }
+            if (end == min) break
+            start = end
+        }
+        return n1 - n2
+    } else {
+        return compareTo(other)
+    }
+}

libraries/stdlib/jvm/src/kotlin/text/StringsJVM.kt

@@ -317,7 +317,7 @@ public inline fun String.codePointCount(beginIndex: Int, endIndex: Int): Int =
 /**
  * Compares two strings lexicographically, optionally ignoring case differences.
  */
-public fun String.compareTo(other: String, ignoreCase: Boolean = false): Int {
+public actual fun String.compareTo(other: String, ignoreCase: Boolean): Int {
     if (ignoreCase)
         return (this as java.lang.String).compareToIgnoreCase(other)
     else

libraries/stdlib/test/text/StringTest.kt

@@ -1336,4 +1336,29 @@ ${"    "}
         assertEquals("  ABC\n   \n  123", "ABC\n   \n123".prependIndent("  "))
         assertEquals("  ", "".prependIndent("  "))
     }
+
+    @Test fun testCompareToIgnoreCase() {
+        assertTrue("ABC".compareTo("ABC", ignoreCase = false) == 0)
+        assertTrue("ABC".compareTo("ABc", ignoreCase = false) < 0)
+        assertTrue("ABc".compareTo("ABC", ignoreCase = false) > 0)
+        assertTrue("ABC".compareTo("ABx", ignoreCase = false) < 0)
+        assertTrue("ABx".compareTo("ABC", ignoreCase = false) > 0)
+        assertTrue("[".compareTo("aa", ignoreCase = false) < 0)
+        assertTrue("".compareTo("", ignoreCase = false) == 0)
+        assertTrue("".compareTo("A", ignoreCase = false) < 0)
+        assertTrue("A".compareTo("", ignoreCase = false) > 0)
+        assertTrue(("A".repeat(16) + "B").compareTo("A".repeat(16) + "b", ignoreCase = false) < 0)
+
+        assertTrue("ABC".compareTo("ABC", ignoreCase = true) == 0)
+        assertTrue("ABC".compareTo("ABc", ignoreCase = true) == 0)
+        assertTrue("ABc".compareTo("ABC", ignoreCase = true) == 0)
+        assertTrue("ABC".compareTo("ABx", ignoreCase = true) < 0)
+        assertTrue("ABx".compareTo("ABC", ignoreCase = true) > 0)
+        assertTrue("[".compareTo("aa", ignoreCase = true) < 0)
+        assertTrue("".compareTo("", ignoreCase = false) == 0)
+        assertTrue("".compareTo("A", ignoreCase = false) < 0)
+        assertTrue("A".compareTo("", ignoreCase = false) > 0)
+        assertTrue(("A".repeat(16) + "B").compareTo("A".repeat(16) + "b", ignoreCase = false) < 0)
+    }
+
 }