serenity/Userland/Libraries/LibJS/Tests/functions/function-evaluation-order.js

describe("CallExpression", () => {
    test("callee is evaluated before arguments", () => {
        function foo() {}
        const values = [];

        [foo][(values.push("callee"), 0)](values.push("args"));

        expect(values).toEqual(["callee", "args"]);
    });

    test("arguments are evaluated in order", () => {
        function foo() {}
        const values = [];

        foo(values.push("arg1"), values.push("arg2"), values.push("arg3"));

        expect(values).toEqual(["arg1", "arg2", "arg3"]);
    });

    test("arguments are evaluated before callee is checked for its type", () => {
        const values = [];

        expect(() => {
            "foo"(values.push("args"));
        }).toThrowWithMessage(TypeError, "foo is not a function");
        expect(values).toEqual(["args"]);

        expect(() => {
            "foo"(bar);
        }).toThrowWithMessage(ReferenceError, "'bar' is not defined");
    });
});

describe("NewExpression", () => {
    test("callee is evaluated before arguments", () => {
        function Foo() {}
        const values = [];

        new [Foo][(values.push("callee"), 0)](values.push("args"));

        expect(values).toEqual(["callee", "args"]);
    });

    test("arguments are evaluated in order", () => {
        function Foo() {}
        const values = [];

        new Foo(values.push("arg1"), values.push("arg2"), values.push("arg3"));

        expect(values).toEqual(["arg1", "arg2", "arg3"]);
    });

    test("arguments are evaluated before callee is checked for its type", () => {
        const values = [];

        expect(() => {
            new "Foo"(values.push("args"));
        }).toThrowWithMessage(TypeError, "Foo is not a constructor");
        expect(values).toEqual(["args"]);

        expect(() => {
            new "Foo"(bar);
        }).toThrowWithMessage(ReferenceError, "'bar' is not defined");
    });
});