如何在TypeScript中表达日期类型?

类型是Date:

const d: Date = new Date(); // but the type can also be inferred from "new Date()" already

这和其他对象实例一样:)

每个类或接口都可以在TypeScript中用作类型。

 const date = new Date();

Date是一个内部TypeScript对象，由DateConstructor接口引用。

对于你使用的构造函数，它被定义为:

interface DateConstructor {
new(): Date;
...
}

为了让它更明确，你可以使用:

 const date: Date = new Date();

不过，你可能会错过类型定义，Date是来自ES6库的示例，在我的tsconfig.json中，我定义了:

"compilerOptions": {
"target": "ES6",
"lib": [
"es6",
"dom"
],

您可以调整这些设置来针对您想要的JavaScript版本。

顺便说一下，Date是lib.es6.d.ts的一个接口:

/** Enables basic storage and retrieval of dates and times. */
interface Date {
/** Returns a string representation of a date. The format of the string depends on the locale. */
toString(): string;
/** Returns a date as a string value. */
toDateString(): string;
/** Returns a time as a string value. */
toTimeString(): string;
/** Returns a value as a string value appropriate to the host environment's current locale. */
toLocaleString(): string;
/** Returns a date as a string value appropriate to the host environment's current locale. */
toLocaleDateString(): string;
/** Returns a time as a string value appropriate to the host environment's current locale. */
toLocaleTimeString(): string;
/** Returns the stored time value in milliseconds since midnight, January 1, 1970 UTC. */
valueOf(): number;
/** Gets the time value in milliseconds. */
getTime(): number;
/** Gets the year, using local time. */
getFullYear(): number;
/** Gets the year using Universal Coordinated Time (UTC). */
getUTCFullYear(): number;
/** Gets the month, using local time. */
getMonth(): number;
/** Gets the month of a Date object using Universal Coordinated Time (UTC). */
getUTCMonth(): number;
/** Gets the day-of-the-month, using local time. */
getDate(): number;
/** Gets the day-of-the-month, using Universal Coordinated Time (UTC). */
getUTCDate(): number;
/** Gets the day of the week, using local time. */
getDay(): number;
/** Gets the day of the week using Universal Coordinated Time (UTC). */
getUTCDay(): number;
/** Gets the hours in a date, using local time. */
getHours(): number;
/** Gets the hours value in a Date object using Universal Coordinated Time (UTC). */
getUTCHours(): number;
/** Gets the minutes of a Date object, using local time. */
getMinutes(): number;
/** Gets the minutes of a Date object using Universal Coordinated Time (UTC). */
getUTCMinutes(): number;
/** Gets the seconds of a Date object, using local time. */
getSeconds(): number;
/** Gets the seconds of a Date object using Universal Coordinated Time (UTC). */
getUTCSeconds(): number;
/** Gets the milliseconds of a Date, using local time. */
getMilliseconds(): number;
/** Gets the milliseconds of a Date object using Universal Coordinated Time (UTC). */
getUTCMilliseconds(): number;
/** Gets the difference in minutes between the time on the local computer and Universal Coordinated Time (UTC). */
getTimezoneOffset(): number;
/**
* Sets the date and time value in the Date object.
* @param time A numeric value representing the number of elapsed milliseconds since midnight, January 1, 1970 GMT.
*/
setTime(time: number): number;
/**
* Sets the milliseconds value in the Date object using local time.
* @param ms A numeric value equal to the millisecond value.
*/
setMilliseconds(ms: number): number;
/**
* Sets the milliseconds value in the Date object using Universal Coordinated Time (UTC).
* @param ms A numeric value equal to the millisecond value.
*/
setUTCMilliseconds(ms: number): number;


/**
* Sets the seconds value in the Date object using local time.
* @param sec A numeric value equal to the seconds value.
* @param ms A numeric value equal to the milliseconds value.
*/
setSeconds(sec: number, ms?: number): number;
/**
* Sets the seconds value in the Date object using Universal Coordinated Time (UTC).
* @param sec A numeric value equal to the seconds value.
* @param ms A numeric value equal to the milliseconds value.
*/
setUTCSeconds(sec: number, ms?: number): number;
/**
* Sets the minutes value in the Date object using local time.
* @param min A numeric value equal to the minutes value.
* @param sec A numeric value equal to the seconds value.
* @param ms A numeric value equal to the milliseconds value.
*/
setMinutes(min: number, sec?: number, ms?: number): number;
/**
* Sets the minutes value in the Date object using Universal Coordinated Time (UTC).
* @param min A numeric value equal to the minutes value.
* @param sec A numeric value equal to the seconds value.
* @param ms A numeric value equal to the milliseconds value.
*/
setUTCMinutes(min: number, sec?: number, ms?: number): number;
/**
* Sets the hour value in the Date object using local time.
* @param hours A numeric value equal to the hours value.
* @param min A numeric value equal to the minutes value.
* @param sec A numeric value equal to the seconds value.
* @param ms A numeric value equal to the milliseconds value.
*/
setHours(hours: number, min?: number, sec?: number, ms?: number): number;
/**
* Sets the hours value in the Date object using Universal Coordinated Time (UTC).
* @param hours A numeric value equal to the hours value.
* @param min A numeric value equal to the minutes value.
* @param sec A numeric value equal to the seconds value.
* @param ms A numeric value equal to the milliseconds value.
*/
setUTCHours(hours: number, min?: number, sec?: number, ms?: number): number;
/**
* Sets the numeric day-of-the-month value of the Date object using local time.
* @param date A numeric value equal to the day of the month.
*/
setDate(date: number): number;
/**
* Sets the numeric day of the month in the Date object using Universal Coordinated Time (UTC).
* @param date A numeric value equal to the day of the month.
*/
setUTCDate(date: number): number;
/**
* Sets the month value in the Date object using local time.
* @param month A numeric value equal to the month. The value for January is 0, and other month values follow consecutively.
* @param date A numeric value representing the day of the month. If this value is not supplied, the value from a call to the getDate method is used.
*/
setMonth(month: number, date?: number): number;
/**
* Sets the month value in the Date object using Universal Coordinated Time (UTC).
* @param month A numeric value equal to the month. The value for January is 0, and other month values follow consecutively.
* @param date A numeric value representing the day of the month. If it is not supplied, the value from a call to the getUTCDate method is used.
*/
setUTCMonth(month: number, date?: number): number;
/**
* Sets the year of the Date object using local time.
* @param year A numeric value for the year.
* @param month A zero-based numeric value for the month (0 for January, 11 for December). Must be specified if numDate is specified.
* @param date A numeric value equal for the day of the month.
*/
setFullYear(year: number, month?: number, date?: number): number;
/**
* Sets the year value in the Date object using Universal Coordinated Time (UTC).
* @param year A numeric value equal to the year.
* @param month A numeric value equal to the month. The value for January is 0, and other month values follow consecutively. Must be supplied if numDate is supplied.
* @param date A numeric value equal to the day of the month.
*/
setUTCFullYear(year: number, month?: number, date?: number): number;
/** Returns a date converted to a string using Universal Coordinated Time (UTC). */
toUTCString(): string;
/** Returns a date as a string value in ISO format. */
toISOString(): string;
/** Used by the JSON.stringify method to enable the transformation of an object's data for JavaScript Object Notation (JSON) serialization. */
toJSON(key?: any): string;
}

Typescript可以开箱即用地识别Date接口——就像处理数字、字符串或自定义类型一样。所以就用:

myDate : Date;

正如其他人提到的，类型是Date。

当你想在编译时强制你确实有一个Date对象时，这种类型非常有用。下面是一个经常犯的错误(忘记new关键字)，我们可以看到它在编译时被捕获。

const date: Date = new Date();


function logDayNumber(date: Date){
console.log(date.getDay())
}


// Works fine
logDayNumber(date);


// Compile time error which happens when you forget new a String we be produced from Date()
// Argument of type 'string' is not assignable to parameter of type 'Date'
logDayNumber(Date());