diff --git a/Libraries/LibJS/Runtime/GlobalObject.cpp b/Libraries/LibJS/Runtime/GlobalObject.cpp index 6ca80cf8a5b..c4bc2b80d18 100644 --- a/Libraries/LibJS/Runtime/GlobalObject.cpp +++ b/Libraries/LibJS/Runtime/GlobalObject.cpp @@ -247,8 +247,13 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_float) auto string = vm.argument(0); // OPTIMIZATION: We can skip the number-to-string-to-number round trip when the value is already a number. - if (string.is_number()) + if (string.is_number()) { + // Special case for negative zero - it should become positive zero + if (string.is_negative_zero()) + return Value(0); + return string; + } // 1. Let inputString be ? ToString(string). auto input_string = TRY(string.to_string(vm)); diff --git a/Libraries/LibJS/Tests/builtins/functions/parseFloat.js b/Libraries/LibJS/Tests/builtins/functions/parseFloat.js index 5f62ec01a47..fa5be6e5b95 100644 --- a/Libraries/LibJS/Tests/builtins/functions/parseFloat.js +++ b/Libraries/LibJS/Tests/builtins/functions/parseFloat.js @@ -1,6 +1,16 @@ +// This is necessary because we can't simply check if 0 is negative using equality, +// since -0 === 0 evaluates to true. +// test262 checks for negative zero in a similar way here: +// https://github.com/tc39/test262/blob/main/test/built-ins/parseFloat/S15.1.2.3_A1_T2.js +function isZeroNegative(x) { + const isZero = x === 0; + const isNegative = 1 / x === Number.NEGATIVE_INFINITY; + + return isZero && isNegative; +} + test("parsing numbers", () => { [ - [0, 0], [1, 1], [0.23, 0.23], [1.23, 1.23], @@ -14,6 +24,16 @@ test("parsing numbers", () => { }); }); +test("parsing zero", () => { + expect(isZeroNegative(parseFloat("0"))).toBeFalse(); + expect(isZeroNegative(parseFloat("+0"))).toBeFalse(); + expect(isZeroNegative(parseFloat("-0"))).toBeTrue(); + + expect(isZeroNegative(parseFloat(0))).toBeFalse(); + expect(isZeroNegative(parseFloat(+0))).toBeFalse(); + expect(isZeroNegative(parseFloat(-0))).toBeFalse(); +}); + test("parsing strings", () => { [ ["0", 0],