object-tostring.js

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function doTest(expected, v) {

    assertEq(Object.prototype.toString.call(v), expected)

function Dummy() {}

// Basic primitive cases

doTest("[object Undefined]", undefined);

doTest("[object Null]", null);

doTest("[object String]", "");

doTest("[object Number]", 12);

doTest("[object Number]", 12.34);

doTest("[object Boolean]", true);

doTest("[object Symbol]", Symbol());

doTest("[object BigInt]", 1234n);

// Exotic objects with builtinTag

doTest("[object Array]", []);

(function() {

    doTest("[object Arguments]", arguments);

})();

doTest("[object Function]", () => {});

doTest("[object Error]", new Error);

doTest("[object Date]", new Date);

doTest("[object RegExp]", /i/);

// Exotic objects with @@toStringTag

doTest("[object Map]", new Map);

doTest("[object Set]", new Set);

doTest("[object JSON]", JSON);

doTest("[object Math]", Math);

// Normal object cases

doTest("[object Object]", {});

doTest("[object Object]", new Dummy);

doTest("[object Foo]", { [Symbol.toStringTag]: "Foo" });

// Test the receiver of Symbol.toStringTag

let receiver1;

let object1 = {

    __proto__: {

        get [Symbol.toStringTag]() {

            receiver1 = this;

};

doTest("[object Object]", object1);

assertEq(receiver1, object1);

//// BELOW THIS LINE TAMPERS WITH GLOBAL

// Set a toStringTag on the global String.prototype

let receiver2;

Object.defineProperty(String.prototype, Symbol.toStringTag, { get: function() {

    receiver2 = this;

    return "XString";

}});

doTest("[object XString]", "");

assertEq(Object.getPrototypeOf(receiver2), String.prototype);