LibJS: Add String.prototype.indexOf position argument

cubiclove · Jun 30, 2021 · 3666889 · 3666889
1 parent a4c1666
commit 3666889
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Showing 2 changed files with 23 additions and 1 deletion.
diff --git a/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp b/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
@@ -284,7 +284,14 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::index_of)
  auto needle = vm.argument(0).to_string(global_object);
  if (vm.exception())
  return {};
- return Value((i32)string->find(needle).value_or(-1));
+ size_t from = 0;
+ if (vm.argument_count() > 1) {
+ double from_argument = vm.argument(1).to_integer_or_infinity(global_object);
+ if (vm.exception())
+ return {};
+ from = clamp(from_argument, static_cast<double>(0), static_cast<double>(string->length()));
+ }
+ return Value((i32)string->find(needle, from).value_or(-1));
 }
 
 // 22.1.3.26 String.prototype.toLowerCase ( ), https://tc39.es/ecma262/#sec-string.prototype.tolowercase

diff --git a/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.indexOf.js b/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.indexOf.js
@@ -5,4 +5,19 @@ test("basic functionality", () => {
 
  expect(s.indexOf("friends")).toBe(6);
  expect(s.indexOf("enemies")).toBe(-1);
+
+ expect(s.indexOf("friends", 0)).toBe(6);
+ expect(s.indexOf("enemies", 0)).toBe(-1);
+
+ expect(s.indexOf("friends", 4)).toBe(6);
+ expect(s.indexOf("friends", 6)).toBe(6);
+ expect(s.indexOf("friends", 7)).toBe(-1);
+ expect(s.indexOf("friends", 8)).toBe(-1);
+
+ expect(s.indexOf("enemies", 2)).toBe(-1);
+ expect(s.indexOf("enemies", 7)).toBe(-1);
+
+ expect(s.indexOf("e")).toBe(1);
+ expect(s.indexOf("e", 0)).toBe(1);
+ expect(s.indexOf("e", 2)).toBe(9);
 });