Symbol.for()

¥Syntax

Symbol.for(key)

¥Parameters

key

字符串，必填。符号的键（也用于符号的描述）。

¥Return value

具有给定键的现有符号（如果找到）；否则，将创建并返回一个新符号。

¥An existing symbol with the given key if found; otherwise, a new symbol is created and returned.

¥Description

与 Symbol() 相比，Symbol.for() 函数创建 全局符号注册表 列表中可用的符号。Symbol.for() 也不一定在每次调用时创建一个新符号，但首先检查具有给定 key 的符号是否已存在于注册表中。在这种情况下，将返回该符号。如果没有找到具有给定键的符号，Symbol.for() 将创建一个新的全局符号。

¥In contrast to Symbol(), the Symbol.for() function creates a symbol available in a global symbol registry list. Symbol.for() does also not necessarily create a new symbol on every call, but checks first if a symbol with the given key is already present in the registry. In that case, that symbol is returned. If no symbol with the given key is found, Symbol.for() will create a new global symbol.

¥Examples

¥Using Symbol.for()

Symbol.for("foo"); // create a new global symbol
Symbol.for("foo"); // retrieve the already created symbol

// Same global symbol, but not locally
Symbol.for("bar") === Symbol.for("bar"); // true
Symbol("bar") === Symbol("bar"); // false

// The key is also used as the description
const sym = Symbol.for("mario");
sym.toString(); // "Symbol(mario)"

为了避免与全局符号键和其他（库代码）全局符号发生名称冲突，最好为符号添加前缀：

¥To avoid name clashes with your global symbol keys and other (library code) global symbols, it might be a good idea to prefix your symbols:

Symbol.for("mdn.foo");
Symbol.for("mdn.bar");

¥See also

• Symbol.keyFor()