我试图运行这段简单的代码:
let FUNJECTOR_KEY = Symbol.for('funjector')
但我一直收到错误消息 — 无法找到名称“Symbol”。
我是TypeScript的新手,所以我不确定是否需要包含某些内容?
在我的情况下,我不想使用polyfill,如此处所述—在TypeScript中使用ES6符号
我试图运行这段简单的代码:
let FUNJECTOR_KEY = Symbol.for('funjector')
但我一直收到错误消息 — 无法找到名称“Symbol”。
我是TypeScript的新手,所以我不确定是否需要包含某些内容?
在我的情况下,我不想使用polyfill,如此处所述—在TypeScript中使用ES6符号
TypeScript编译器将TS转换为JS。在es5模式下,TSC找不到Symbol
的声明。因此,您的错误纯粹是编译时错误。您不需要运行时的polyfill。
为了解决这个问题,您可以将编译目标更改为es6
,这样Symbol
就会在标准库中定义。或者您可以手动添加定义(来源)。
declare class Symbol {
/** Returns a string representation of an object. */
toString(): string;
/** Returns the primitive value of the specified object. */
valueOf(): Object;
/**
* Returns a new unique Symbol value.
* @param description Description of the new Symbol object.
*/
constructor(description?: string);
/**
* Returns a Symbol object from the global symbol registry matching the given key if found.
* Otherwise, returns a new symbol with this key.
* @param key key to search for.
*/
static for(key: string): Symbol;
/**
* Returns a key from the global symbol registry matching the given Symbol if found.
* Otherwise, returns a undefined.
* @param sym Symbol to find the key for.
*/
static keyFor(sym: Symbol): string;
}
// Well-known Symbols
declare module Symbol {
/**
* A method that determines if a constructor object recognizes an object as one of the
* constructor’s instances.Called by the semantics of the instanceof operator.
*/
const hasInstance: Symbol;
/**
* A Boolean value that if true indicates that an object should be flatten to its array
* elements by Array.prototype.concat.
*/
const isConcatSpreadable: Symbol;
/**
* A Boolean value that if true indicates that an object may be used as a regular expression.
*/
const isRegExp: Symbol;
/**
* A method that returns the default iterator for an object.Called by the semantics of the
* for-of statement.
*/
const iterator: Symbol;
/**
* A method that converts an object to a corresponding primitive value.Called by the
* ToPrimitive abstract operation.
*/
const toPrimitive: Symbol;
/**
* A String value that is used in the creation of the default string description of an object.
* Called by the built- in method Object.prototype.toString.
*/
const toStringTag: Symbol;
/**
* An Object whose own property names are property names that are excluded from the with
* environment bindings of the associated objects.
*/
const unscopables: Symbol;
}
Symbol
的限制 https://github.com/Microsoft/TypeScript/issues/5579 - Herrington Darkholme