LibJS: Add Number.prototype.toString

Author: https://github.com/mattco98
Commit: https://github.com/SerenityOS/serenity/commit/02305d01ea8
Pull-request: https://github.com/SerenityOS/serenity/pull/2802
Reviewed-by: https://github.com/awesomekling ✅

Libraries/LibJS/Runtime/ErrorTypes.h

@@ -45,6 +45,7 @@
     M(InstanceOfOperatorBadPrototype, "'prototype' property of %s is not an object")                   \
     M(InvalidAssignToConst, "Invalid assignment to const variable")                                    \
     M(InvalidLeftHandAssignment, "Invalid left-hand side in assignment")                               \
+    M(InvalidRadix, "Radix must be an integer no less than 2, and no greater than 36")                 \
     M(IsNotA, "%s is not a %s")                                                                        \
     M(IsNotAEvaluatedFrom, "%s is not a %s (evaluated from '%s')")                                     \
     M(IterableNextBadReturn, "iterator.next() returned a non-object value")                            \
@@ -62,6 +63,7 @@
     M(NotASymbol, "%s is not a symbol")                                                                \
     M(NotIterable, "%s is not iterable")                                                               \
     M(NonExtensibleDefine, "Cannot define property %s on non-extensible object")                       \
+    M(NumberIncompatibleThis, "Number.prototype.%s method called with incompatible this target")       \
     M(ObjectDefinePropertyReturnedFalse, "Object's [[DefineProperty]] method returned false")          \
     M(ObjectSetPrototypeOfReturnedFalse, "Object's [[SetPrototypeOf]] method returned false")          \
     M(ObjectSetPrototypeOfTwoArgs, "Object.setPrototypeOf requires at least two arguments")            \

Libraries/LibJS/Runtime/NumberObject.h

@@ -42,6 +42,8 @@ public:
     virtual bool is_number_object() const override { return true; }
     virtual Value value_of() const override { return Value(m_value); }
 
+    double number() const { return m_value; }
+
 private:
     double m_value { 0 };
 };

Libraries/LibJS/Runtime/NumberPrototype.cpp

@@ -25,18 +25,117 @@
  */
 
 #include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/Error.h>
 #include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/NumberObject.h>
 #include <LibJS/Runtime/NumberPrototype.h>
 
 namespace JS {
 
+static const u8 max_precision_for_radix[37] = {
+    0,  0,  52, 32, 26, 22, 20, 18, 17, 16,
+    15, 15, 14, 14, 13, 13, 13, 12, 12, 12,
+    12, 11, 11, 11, 11, 11, 11, 10, 10, 10,
+    10, 10, 10, 10, 10, 10, 10,
+};
+
+static char digits[] = "0123456789abcdefghijklmnopqrstuvwxyz";
+
 NumberPrototype::NumberPrototype(GlobalObject& global_object)
     : NumberObject(0, *global_object.object_prototype())
 {
 }
 
+void NumberPrototype::initialize(Interpreter& interpreter, GlobalObject& object)
+{
+    Object::initialize(interpreter, object);
+
+    define_native_function("toString", to_string, 1, Attribute::Configurable | Attribute::Writable);
+}
+
 NumberPrototype::~NumberPrototype()
 {
 }
 
+JS_DEFINE_NATIVE_FUNCTION(NumberPrototype::to_string)
+{
+    Value number_value;
+
+    auto this_value = interpreter.this_value(global_object);
+    if (this_value.is_number()) {
+        number_value = this_value;
+    } else if (this_value.is_object() && this_value.as_object().is_number_object()) {
+        number_value = static_cast<NumberObject&>(this_value.as_object()).value_of();
+    } else {
+        return interpreter.throw_exception<TypeError>(ErrorType::NumberIncompatibleThis, "toString");
+    }
+
+    int radix;
+    auto argument = interpreter.argument(0);
+    if (argument.is_undefined()) {
+        radix = 10;
+    } else {
+        radix = argument.to_i32(interpreter);
+    }
+
+    if (interpreter.exception() || radix < 2 || radix > 36)
+        return interpreter.throw_exception<RangeError>(ErrorType::InvalidRadix);
+
+    if (number_value.is_positive_infinity())
+        return js_string(interpreter, "Infinity");
+    if (number_value.is_negative_infinity())
+        return js_string(interpreter, "-Infinity");
+    if (number_value.is_nan())
+        return js_string(interpreter, "NaN");
+    if (number_value.is_positive_zero() || number_value.is_negative_zero())
+        return js_string(interpreter, "0");
+
+    double number = number_value.as_double();
+    bool negative = number < 0;
+    if (negative)
+        number *= -1;
+
+    int int_part = floor(number);
+    double decimal_part = number - int_part;
+
+    Vector<char> backwards_characters;
+
+    if (int_part == 0) {
+        backwards_characters.append('0');
+    } else {
+        while (int_part > 0) {
+            backwards_characters.append(digits[int_part % radix]);
+            int_part /= radix;
+        }
+    }
+
+    Vector<char> characters;
+    if (negative)
+        characters.append('-');
+
+    // Reverse characters;
+    for (ssize_t i = backwards_characters.size() - 1; i >= 0; --i) {
+        characters.append(backwards_characters[i]);
+    }
+
+    // decimal part
+    if (decimal_part != 0.0) {
+        characters.append('.');
+
+        int precision = max_precision_for_radix[radix];
+
+        for (int i = 0; i < precision; ++i) {
+            decimal_part *= radix;
+            int integral = floor(decimal_part);
+            characters.append(digits[integral]);
+            decimal_part -= integral;
+        }
+
+        while (characters.last() == '0')
+            characters.take_last();
+    }
+
+    return js_string(interpreter, String(characters.data(), characters.size()));
+}
+
 }

Libraries/LibJS/Runtime/NumberPrototype.h

@@ -35,7 +35,10 @@ class NumberPrototype final : public NumberObject {
 
 public:
     explicit NumberPrototype(GlobalObject&);
+    virtual void initialize(Interpreter&, GlobalObject&) override;
     virtual ~NumberPrototype() override;
+
+    JS_DECLARE_NATIVE_FUNCTION(to_string);
 };
 
 }

Libraries/LibJS/Tests/builtins/Array/Array.prototype.toLocaleString.js

@@ -15,10 +15,6 @@ describe("normal behavior", () => {
         expect(["foo", "bar", "baz"].toLocaleString()).toBe("foo,bar,baz");
     });
 
-    test("number stringification differs from regular toString, for now", () => {
-        expect([1, 2, 3].toLocaleString()).toBe("[object Number],[object Number],[object Number]");
-    });
-
     test("null and undefined result in empty strings", () => {
         expect([null].toLocaleString()).toBe("");
         expect([undefined].toLocaleString()).toBe("");

Libraries/LibJS/Tests/builtins/Number/Number.prototype.toString.js

@@ -0,0 +1,83 @@
+describe("correct behavior", () => {
+    test("length", () => {
+        expect(Number.prototype.toString).toHaveLength(1);
+    });
+
+    test("basic functionality", () => {
+        [
+            [+0, "0"],
+            [-0, "0"],
+            [Infinity, "Infinity"],
+            [-Infinity, "-Infinity"],
+            [NaN, "NaN"],
+            [12, "12"],
+            [93465, "93465"],
+            [358000, "358000"],
+        ].forEach(testCase => {
+            expect(testCase[0].toString()).toBe(testCase[1]);
+        });
+    });
+
+    test("radix", () => {
+        let number = 7857632;
+
+        [
+            [2, "11101111110010111100000"],
+            [3, "112210012122102"],
+            [4, "131332113200"],
+            [5, "4002421012"],
+            [6, "440225532"],
+            [7, "123534356"],
+            [8, "35762740"],
+            [9, "15705572"],
+            [10, "7857632"],
+            [11, "4487612"],
+            [12, "276b2a8"],
+            [13, "18216b3"],
+            [14, "10877d6"],
+            [15, "a532c2"],
+            [16, "77e5e0"],
+            [17, "59160b"],
+            [18, "42f5h2"],
+            [19, "335b5b"],
+            [20, "29241c"],
+            [21, "1j89fk"],
+            [22, "1bbkh2"],
+            [23, "151ih4"],
+            [24, "ng9h8"],
+            [25, "k2m57"],
+            [26, "h51ig"],
+            [27, "el5hb"],
+            [28, "clqdk"],
+            [29, "b355o"],
+            [30, "9l0l2"],
+            [31, "8fng0"],
+            [32, "7fpf0"],
+            [33, "6klf2"],
+            [34, "5tv8s"],
+            [35, "589dr"],
+            [36, "4oezk"],
+        ].forEach(testCase => {
+            expect(number.toString(testCase[0])).toBe(testCase[1]);
+        });
+    });
+
+    test("decimal radix gets converted to int", () => {
+        expect((30).toString(10.1)).toBe("30");
+        expect((30).toString(10.9)).toBe("30");
+    });
+});
+
+test("errors", () => {
+    test("must be called with numeric |this|", () => {
+        [true, [], {}, Symbol("foo"), "bar", 1n].forEach(value => {
+            expect(() => Number.prototype.toString.call(value)).toThrow(TypeError);
+        });
+    });
+
+    test("radix RangeError", () => {
+        [0, 1, 37, 100].forEach(value => {
+            expect(() => (0).toString(value)).toThrow(RangeError);
+        });
+    });
+});