WeakMap.prototype.has()
Baseline
Widely available
This feature is well established and works across many devices and browser versions. Itâs been available across browsers since иÑÐ»Ñ 2015 г..
ÐеÑод has() возвÑаÑÐ°ÐµÑ Ð±Ñлевое знаÑение, коÑоÑое ÑказÑÐ²Ð°ÐµÑ Ð½Ð° Ñо ÑÑÑеÑÑвÑÐµÑ ÑÐ»ÐµÐ¼ÐµÐ½Ñ Ñ Ñаким клÑÑом в обÑекÑе WeakMap или неÑ.
СинÑакÑиÑ
wm.has(key);
ÐаÑамеÑÑÑ
- key
-
ÐбÑзаÑелен. ÐлÑÑ ÑлеменÑа, ÑÑÑеÑÑвование коÑоÑого Ð½ÐµÐ¾Ð±Ñ Ð¾Ð´Ð¸Ð¼Ð¾ пÑовеÑиÑÑ Ð² обÑекÑе WeakMap.
ÐозвÑаÑаемое знаÑение
- Boolean
-
ÐозвÑаÑаеÑ
trueеÑли ÑÐ»ÐµÐ¼ÐµÐ½Ñ Ñ ÑказаннÑм клÑÑом ÑÑÑеÑÑвÑÐµÑ Ð² обÑекÑе WeakMap, еÑли Ð½ÐµÑ â false.
ÐÑимеÑÑ
ÐÑполÑзование меÑода has
js
var wm = new WeakMap();
wm.set(window, "foo");
wm.has(window); // возвÑаÑÐ°ÐµÑ true
wm.has("baz"); // возвÑаÑÐ°ÐµÑ false
СпеÑиÑикаÑии
| Specification |
|---|
| ECMAScript® 2027 Language Specification # sec-weakmap.prototype.has |
СовмеÑÑимоÑÑÑ Ñ Ð±ÑаÑзеÑами
Firefox-specific notes
- Prior to SpiderMonkey 38, this method threw a
TypeErrorwhen thekeyparameter was not an object. This has been fixed in version 38 and later to returnfalseas per latest ES6 standard (Firefox bug 1127827).