toPrimitive-callers.js

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// Check all the algorithms that call ToPrimitive. Confirm that they're passing

// the correct hint, per spec.

var STRING = "xyzzy";

var NUMBER = 42;

function assertCallsToPrimitive(f, expectedHint, expectedResult) {

    var hint = undefined;

    var testObj = {

        [Symbol.toPrimitive](h) {

            assertEq(hint, undefined);

            hint = h;

            return h === "number" ? NUMBER : STRING;

};

    var result = f(testObj);

    assertEq(hint, expectedHint, String(f));

    assertEq(result, expectedResult, String(f));

// ToNumber

assertCallsToPrimitive(Number, "number", NUMBER);

// ToString

assertCallsToPrimitive(String, "string", STRING);

// ToPropertyKey

var obj = {[STRING]: "pass"};

assertCallsToPrimitive(key => obj[key], "string", "pass");

// Abstract Relational Comparison

assertCallsToPrimitive(x => x >= 42, "number", true);

assertCallsToPrimitive(x => x > "42", "number", false);

// Abstract Equality Comparison

assertCallsToPrimitive(x => x != STRING, "default", false);

assertCallsToPrimitive(x => STRING == x, "default", true);

assertCallsToPrimitive(x => x == NUMBER, "default", false);

assertCallsToPrimitive(x => NUMBER != x, "default", true);

// Addition

assertCallsToPrimitive(x => 1 + x, "default", "1" + STRING);

assertCallsToPrimitive(x => "" + x, "default", STRING);

// Date constructor

assertCallsToPrimitive(x => (new Date(x)).valueOf(), "default", Number(STRING));

// Date.prototype.toJSON

var expected = "a suffusion of yellow";

function testJSON(x) {

    x.toJSON = Date.prototype.toJSON;

    x.toISOString = function () { return expected; };

    return JSON.stringify(x);

assertCallsToPrimitive(testJSON, "number", JSON.stringify(expected));

reportCompare(0, 0);