JavaScript weakMap.has()方法用法示例 _JavaScript

以下是示例weakMap.has()方法。

< script> function gfg() { const weakmap = new WeakMap(); const key = {}; weakmap.set(key, 'gfg' ); document.write(weakmap.has(key)); } gfg(); < /script>

输出如下： true
weakMap.has()是JavaScript中的内置函数, 用于返回布尔值, 该布尔值指示在弱映射对象中是否存在具有特定键的元素。
语法如下：

weakMap.has(key);

参数：它接受参数" key", 该参数是要测试的对象弱映射中是否存在的元素的键。
返回值：如果弱映射对象中存在具有指定键的元素, 则返回true, 否则返回false。
例子：

Input: weakmap1.has(key1) Output: true

JavaScript, 显示此功能的工作原理：
代码1：

< script> //Creating a WeakMap() object const weakmap1 = new WeakMap(); //Creating a key "key1" const key1 = {}; //setting element 'gfg' to the key "key1" weakmap1.set(key1, 'gfg' ); //Testing whether the key is present //in the weakMap() object or not document.write(weakmap1.has(key1)); < /script>

输出如下：

true

代码2：

< script> //Creating a WeakMap() object const weakmap1 = new WeakMap(); //Creating a key "key1" const key1 = {}; //Testing whether the key is present //in the weakMap() object or not document.write(weakmap1.has(key1)); < /script>

输出如下：