Why not set bound.prototype = target.prototype directly? #463

LongTengDao · 2019-06-25T16:44:58Z

Line 307 in d5297ad

bound.prototype = new Empty();

function f () {}
var b = f.bind({});
new f instanceof b;// true in native, but false in shim

ljharb · 2019-06-25T17:57:42Z

When I overwrite Function.prototype.bind in my current browser with the shim's implementation, new f instanceof b returns true for me. In what browser are you seeing it return false?

ljharb · 2019-06-25T17:58:20Z

(Note that it would be incorrect to set it directly; b.prototype !== f.prototype in native)

LongTengDao · 2019-06-26T00:27:26Z

<!DOCTYPE html>
<html>
	<head>
		<title></title>
		<script src="./es5-shim.js"></script>
	</head>
	<body>
		<script>
			function F () {}
			var B = F.bind([]);
			var f = new F;
			document.write(f instanceof B);
		</script>
	</body>
</html>

IE 6 7 8 all print false.

In current shim, B.prototype is instance of F, in other words, new F and B.prototype are same level instance.

(! ( B.prototype instanceof F ) in native too)

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Why not set bound.prototype = target.prototype directly? #463

Why not set bound.prototype = target.prototype directly? #463

LongTengDao commented Jun 25, 2019

ljharb commented Jun 25, 2019

ljharb commented Jun 25, 2019 •

edited

LongTengDao commented Jun 26, 2019 •

edited

Why not set bound.prototype = target.prototype directly? #463

Why not set bound.prototype = target.prototype directly? #463

Comments

LongTengDao commented Jun 25, 2019

ljharb commented Jun 25, 2019

ljharb commented Jun 25, 2019 • edited

LongTengDao commented Jun 26, 2019 • edited

ljharb commented Jun 25, 2019 •

edited

LongTengDao commented Jun 26, 2019 •

edited