diff --git a/js/js.libraries/src/core/char.kt b/js/js.libraries/src/core/char.kt
index 22f7c70d9ee..b6aab56c24a 100644
--- a/js/js.libraries/src/core/char.kt
+++ b/js/js.libraries/src/core/char.kt
@@ -18,3 +18,7 @@ package kotlin.js
 
 // actually \s is enough to match all whitespace, but \xA0 added because of different regexp behavior of Rhino used in Selenium tests
 public fun Char.isWhitespace(): Boolean = toString().matches("[\\s\\xA0]")
+
+native public fun Char.toLowerCase(): Char = noImpl
+
+native public fun Char.toUpperCase(): Char = noImpl
diff --git a/js/js.libraries/src/core/string.kt b/js/js.libraries/src/core/string.kt
index 74b2e9aaeeb..dae143b03b6 100644
--- a/js/js.libraries/src/core/string.kt
+++ b/js/js.libraries/src/core/string.kt
@@ -1,28 +1,20 @@
 package kotlin.js
 
-native public fun String.startsWith(s: String): Boolean = noImpl
-native public fun String.endsWith(s: String): Boolean = noImpl
-native public fun String.contains(s: String): Boolean = noImpl
-
-native public fun String.startsWith(char: Char): Boolean = noImpl
-native public fun String.endsWith(char: Char): Boolean = noImpl
-native public fun String.contains(char: Char): Boolean = noImpl
-
 native public fun String.toUpperCase() : String = noImpl
 
 native public fun String.toLowerCase() : String = noImpl
 
-native public fun String.indexOf(str : String) : Int = noImpl
-native public fun String.indexOf(str : String, fromIndex : Int) : Int = noImpl
+native("indexOf")
+public fun String.nativeIndexOf(str : String, fromIndex : Int) : Int = noImpl
 
-native public fun String.lastIndexOf(str: String) : Int = noImpl
-native public fun String.lastIndexOf(str : String, fromIndex : Int) : Int = noImpl
+native("lastIndexOf")
+public fun String.nativeLastIndexOf(str : String, fromIndex : Int) : Int = noImpl
 
 library("splitString")
-public fun String.split(regex: String): Array<String> = noImpl
+public fun String.splitByRegex(regex: String): Array<String> = noImpl
 
 library("splitString")
-public fun String.split(regex: String, limit: Int): Array<String> = noImpl
+public fun String.splitByRegex(regex: String, limit: Int): Array<String> = noImpl
 
 native public fun String.substring(beginIndex : Int) : String = noImpl
 native public fun String.substring(beginIndex : Int, endIndex : Int) : String = noImpl
diff --git a/js/js.libraries/src/core/stringsCode.kt b/js/js.libraries/src/core/stringsCode.kt
index 706f448b1b9..68dc1d15afe 100644
--- a/js/js.libraries/src/core/stringsCode.kt
+++ b/js/js.libraries/src/core/stringsCode.kt
@@ -1,16 +1,50 @@
 package kotlin.js
 
-public inline fun String.lastIndexOf(ch : Char, fromIndex : Int) : Int = lastIndexOf(ch.toString(), fromIndex)
-public inline fun String.lastIndexOf(ch: Char) : Int = lastIndexOf(ch.toString())
+public inline fun String.nativeIndexOf(ch : Char, fromIndex : Int) : Int = nativeIndexOf(ch.toString(), fromIndex)
+public inline fun String.nativeLastIndexOf(ch : Char, fromIndex : Int) : Int = nativeLastIndexOf(ch.toString(), fromIndex)
+
+/**
+ * Returns `true` if this string starts with the specified prefix.
+ */
+public fun String.startsWith(prefix: String, ignoreCase: Boolean = false): Boolean =
+        regionMatches(0, prefix, 0, prefix.length(), ignoreCase)
+
+/**
+ * Returns `true` if a substring of this string starting at the specified offset [thisOffset] starts with the specified prefix.
+ */
+public fun String.startsWith(prefix: String, thisOffset: Int, ignoreCase: Boolean = false): Boolean =
+        regionMatches(thisOffset, prefix, 0, prefix.length(), ignoreCase)
+
+/**
+ * Returns `true` if this string ends with the specified suffix.
+ */
+public fun String.endsWith(suffix: String, ignoreCase: Boolean = false): Boolean =
+        regionMatches(length() - suffix.length(), suffix, 0, suffix.length(), ignoreCase = true)
+
 
-public inline fun String.indexOf(ch : Char) : Int = indexOf(ch.toString())
-public inline fun String.indexOf(ch : Char, fromIndex : Int) : Int = indexOf(ch.toString(), fromIndex)
 
 public inline fun String.matches(regex : String) : Boolean {
     val result = this.match(regex)
     return result != null && result.size() > 0
 }
 
+public fun String.equals(anotherString: String, ignoreCase: Boolean = false): Boolean =
+        if (!ignoreCase)
+            this == anotherString
+        else
+            this.toLowerCase() == anotherString.toLowerCase()
+
+
+public fun String.regionMatches(thisOffset: Int, other: String, otherOffset: Int, length: Int, ignoreCase: Boolean = false): Boolean {
+    if ((otherOffset < 0) || (thisOffset < 0) || (thisOffset > length() - length)
+        || (otherOffset > other.length() - length)) {
+        return false;
+    }
+
+    return substring(thisOffset, thisOffset + length).equals(other.substring(otherOffset, otherOffset + length), ignoreCase)
+}
+
+
 /**
  * Returns a copy of this string capitalised if it is not empty or already starting with an uppper case letter, otherwise returns this
  *
diff --git a/js/js.translator/testData/kotlin_lib.js b/js/js.translator/testData/kotlin_lib.js
index c3e4f3b1d0d..1027621d12e 100644
--- a/js/js.translator/testData/kotlin_lib.js
+++ b/js/js.translator/testData/kotlin_lib.js
@@ -17,19 +17,6 @@
 (function (Kotlin) {
     "use strict";
 
-    // Shims for String
-    String.prototype.startsWith = function (s) {
-        return this.indexOf(s) === 0;
-    };
-
-    String.prototype.endsWith = function (s) {
-        return this.indexOf(s, this.length - s.length) !== -1;
-    };
-
-    String.prototype.contains = function (s) {
-        return this.indexOf(s) !== -1;
-    };
-
     // Kotlin stdlib
 
     Kotlin.equals = function (obj1, obj2) {