plain-object-to-string.js

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// Test for OrdinaryToPrimitive called on a plain object with hint "string".

function assertStr(o, s) {

  assertEq(String(o), s);

function test() {

  assertStr({x: 1}, "[object Object]");

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

  assertStr({toString() { return 123; }}, "123");

  assertStr({toString: Math.abs}, "NaN");

  assertStr({x: "hello", toString() { return this.x; }}, "hello");

  let c = 0;

  let fun = () => "hi-" + ++c;

  assertStr({toString: fun}, "hi-1");

  assertStr({toString: "foo", valueOf: fun}, "hi-2");

  assertStr({toString() { return {}; }, valueOf: fun}, "hi-3");

  let proto = {};

  proto[Symbol.toStringTag] = null;

  assertStr(Object.create(proto), "[object Object]");

  proto[Symbol.toStringTag] = "Bar";

  assertStr(Object.create(proto), "[object Bar]");

test();