LibJS: Implement String.prototype.endsWith()

Author: https://github.com/XavierCooney
Commit: https://github.com/SerenityOS/serenity/commit/1cf92d39ebc
Pull-request: https://github.com/SerenityOS/serenity/pull/4507
Reviewed-by: https://github.com/linusg ✅

Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -93,6 +93,7 @@ namespace JS {
     P(description)                           \
     P(done)                                  \
     P(dotAll)                                \
+    P(endsWith)                              \
     P(entries)                               \
     P(enumerable)                            \
     P(error)                                 \

Libraries/LibJS/Runtime/StringPrototype.cpp

@@ -75,6 +75,7 @@ void StringPrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.charCodeAt, char_code_at, 1, attr);
     define_native_function(vm.names.repeat, repeat, 1, attr);
     define_native_function(vm.names.startsWith, starts_with, 1, attr);
+    define_native_function(vm.names.endsWith, ends_with, 1, attr);
     define_native_function(vm.names.indexOf, index_of, 1, attr);
     define_native_function(vm.names.toLowerCase, to_lowercase, 0, attr);
     define_native_function(vm.names.toUpperCase, to_uppercase, 0, attr);
@@ -185,6 +186,51 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::starts_with)
     return Value(string.substring(start, search_string_length) == search_string);
 }
 
+JS_DEFINE_NATIVE_FUNCTION(StringPrototype::ends_with)
+{
+    auto string = ak_string_from(vm, global_object);
+    if (string.is_null())
+        return {};
+
+    auto search_string_value = vm.argument(0);
+
+    bool search_is_regexp = search_string_value.is_regexp(global_object);
+    if (vm.exception())
+        return {};
+    if (search_is_regexp) {
+        vm.throw_exception<TypeError>(global_object, ErrorType::IsNotA, "searchString", "string, but a regular expression");
+        return {};
+    }
+
+    auto search_string = search_string_value.to_string(global_object);
+    if (vm.exception())
+        return {};
+
+    auto string_length = string.length();
+    auto search_string_length = search_string.length();
+
+    size_t pos = string_length;
+
+    auto end_position_value = vm.argument(1);
+    if (!end_position_value.is_undefined()) {
+        auto number = end_position_value.to_number(global_object);
+        if (vm.exception())
+            return {};
+        double pos_as_double = number.to_integer_or_infinity(global_object);
+        if (vm.exception())
+            return {};
+        pos = clamp(pos_as_double, static_cast<double>(0), static_cast<double>(string_length));
+    }
+
+    if (search_string_length == 0)
+        return Value(true);
+    if (pos < search_string_length)
+        return Value(false);
+
+    auto start = pos - search_string_length;
+    return Value(string.substring(start, search_string_length) == search_string);
+}
+
 JS_DEFINE_NATIVE_FUNCTION(StringPrototype::index_of)
 {
     auto string = ak_string_from(vm, global_object);

Libraries/LibJS/Runtime/StringPrototype.h

@@ -43,6 +43,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(char_code_at);
     JS_DECLARE_NATIVE_FUNCTION(repeat);
     JS_DECLARE_NATIVE_FUNCTION(starts_with);
+    JS_DECLARE_NATIVE_FUNCTION(ends_with);
     JS_DECLARE_NATIVE_FUNCTION(index_of);
     JS_DECLARE_NATIVE_FUNCTION(to_lowercase);
     JS_DECLARE_NATIVE_FUNCTION(to_uppercase);

Libraries/LibJS/Tests/builtins/String/String.prototype-generic-functions.js

@@ -4,6 +4,7 @@ test("basic functionality", () => {
         "charCodeAt",
         "repeat",
         "startsWith",
+        "endsWith",
         "indexOf",
         "toLowerCase",
         "toUpperCase",

Libraries/LibJS/Tests/builtins/String/String.prototype.endsWith.js

@@ -0,0 +1,39 @@
+test("basic functionality", () => {
+    expect(String.prototype.endsWith).toHaveLength(1);
+
+    var s = "foobar";
+    expect(s.endsWith("r")).toBeTrue();
+    expect(s.endsWith("ar")).toBeTrue();
+    expect(s.endsWith("bar")).toBeTrue();
+    expect(s.endsWith("obar")).toBeTrue();
+    expect(s.endsWith("oobar")).toBeTrue();
+    expect(s.endsWith("foobar")).toBeTrue();
+    expect(s.endsWith("1foobar")).toBeFalse();
+    expect(s.endsWith("r", 6)).toBeTrue();
+    expect(s.endsWith("ar", 6)).toBeTrue();
+    expect(s.endsWith("bar", 6)).toBeTrue();
+    expect(s.endsWith("obar", 6)).toBeTrue();
+    expect(s.endsWith("oobar", 6)).toBeTrue();
+    expect(s.endsWith("foobar", 6)).toBeTrue();
+    expect(s.endsWith("1foobar", 6)).toBeFalse();
+    expect(s.endsWith("bar", [])).toBeFalse();
+    expect(s.endsWith("bar", null)).toBeFalse();
+    expect(s.endsWith("bar", false)).toBeFalse();
+    expect(s.endsWith("bar", true)).toBeFalse();
+    expect(s.endsWith("f", true)).toBeTrue();
+    expect(s.endsWith("bar", -1)).toBeFalse();
+    expect(s.endsWith("bar", 42)).toBeTrue();
+    expect(s.endsWith("foo", 3)).toBeTrue();
+    expect(s.endsWith("foo", "3")).toBeTrue();
+    expect(s.endsWith("foo1", 3)).toBeFalse();
+    expect(s.endsWith("foo", 3.7)).toBeTrue();
+    expect(s.endsWith()).toBeFalse();
+    expect(s.endsWith("")).toBeTrue();
+    expect(s.endsWith("", 0)).toBeTrue();
+    expect(s.endsWith("", 1)).toBeTrue();
+    expect(s.endsWith("", -1)).toBeTrue();
+    expect(s.endsWith("", 42)).toBeTrue();
+    expect("12undefined".endsWith()).toBeTrue();
+    expect(() => s.endsWith(/foobar/)).toThrowWithMessage(TypeError, "searchString is not a string, but a regular expression");
+    expect(s.endsWith("bar", undefined)).toBeTrue();
+});