has()
方法對一個指定值元素在 Set
物件中的存在與否回傳一個布林值。
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語法
mySet.has(value);
參數
value
- 要測試是否存在在
Set
中的值。
回傳值
回傳 true
如果給定值存在在 Set
物件中;反之回傳 false
。
Note: 技術上來說,has()
使用了 sameValueZero
算法來判斷給定元素的存在與否。
範例
使用 has
方法
var mySet = new Set();
mySet.add('foo');
mySet.has('foo'); // returns true
mySet.has('bar'); // returns false
var set1 = new Set();
var obj1 = {'key1': 1};
set1.add(obj1);
set1.has(obj1); // returns true
set1.has({'key1': 1}); // returns false because they are different object references
set1.add({'key1': 1}); // now set1 contains 2 entries
規範
規範 | 狀態 | 註 |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Set.prototype.has' in that specification. |
Standard | Initial definition. |
ECMAScript (ECMA-262) The definition of 'Set.prototype.has' in that specification. |
Living Standard |
瀏覽器相容性
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