LibJS: Add String.prototype.lastIndexOf

Libraries/LibJS/Runtime/StringPrototype.cpp

@@ -81,6 +81,7 @@ StringPrototype::StringPrototype()
  put_native_function("substring", substring, 2, attr);
  put_native_function("includes", includes, 1, attr);
  put_native_function("slice", slice, 2, attr);
+ put_native_function("lastIndexOf", last_index_of, 1, attr);
 }
 
 StringPrototype::~StringPrototype()
@@ -425,4 +426,37 @@ Value StringPrototype::slice(Interpreter& interpreter)
  return js_string(interpreter, string_part);
 }
 
+Value StringPrototype::last_index_of(Interpreter& interpreter)
+{
+ auto string = string_from(interpreter);
+ if (string.is_null())
+ return {};
+
+ if (interpreter.argument_count() == 0)
+ return Value(-1);
+
+ auto search_string = interpreter.argument(0).to_string();
+ if (search_string.length() > string.length())
+ return Value(-1);
+
+ ssize_t max_index = string.length() - search_string.length();
+ ssize_t from_index = max_index;
+ if (interpreter.argument_count() >= 2) {
+ from_index = static_cast<ssize_t>(interpreter.argument(1).to_i32());
+
+ if (from_index < 0)
+ from_index = 0;
+ if (from_index > max_index)
+ from_index = max_index;
+ }
+
+ for (ssize_t i = from_index; i >= 0; --i) {
+ auto part_view = string.substring_view(i, search_string.length());
+ if (part_view == search_string)
+ return Value((i32)i);
+ }
+
+ return Value(-1);
+}
+
 }

Libraries/LibJS/Runtime/StringPrototype.h

@@ -57,6 +57,7 @@ class StringPrototype final : public StringObject {
  static Value concat(Interpreter&);
  static Value includes(Interpreter&);
  static Value slice(Interpreter&);
+ static Value last_index_of(Interpreter&);
 };
 
 }

Libraries/LibJS/Tests/String.prototype.lastIndexOf.js

@@ -0,0 +1,27 @@
+load("test-common.js");
+
+try {
+ assert(String.prototype.lastIndexOf.length === 1);
+ assert("hello friends".lastIndexOf() === -1);
+ assert("hello friends".lastIndexOf("e") === 9);
+ assert("hello friends".lastIndexOf("e", -7) === -1);
+ assert("hello friends".lastIndexOf("e", 100) === 9);
+ assert("hello friends".lastIndexOf("") === 13);
+ assert("hello friends".lastIndexOf("Z") === -1);
+ assert("hello friends".lastIndexOf("serenity") === -1);
+ assert("hello friends".lastIndexOf("", 4) === 4);
+ assert("hello serenity friends".lastIndexOf("serenity") === 6);
+ assert("hello serenity friends serenity".lastIndexOf("serenity") === 23);
+ assert("hello serenity friends serenity".lastIndexOf("serenity", 14) === 6);
+ assert("".lastIndexOf("") === 0);
+ assert("".lastIndexOf("", 1) === 0);
+ assert("".lastIndexOf("", -1) === 0);
+ assert("hello friends serenity".lastIndexOf("h", 10) === 0);
+ assert("hello friends serenity".lastIndexOf("l", 4) === 3);
+ assert("hello friends serenity".lastIndexOf("s", 13) === 12);
+ assert("hello".lastIndexOf("serenity") === -1);
+
+ console.log("PASS");
+} catch (err) {
+ console.log("FAIL: " + err);
+}