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• 句法
• 描述
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

finally() method returns a Promise . When the promise is settled, i.e either fulfilled or rejected, the specified callback function is executed. This provides a way for code to be run whether the promise was fulfilled successfully or rejected once the Promise has been dealt with.

This helps to avoid duplicating code in both the promise's then() and catch() handlers.

句法

p.finally(onFinally);
p.finally(function() {
   // settled (fulfilled or rejected)
});
					

参数

onFinally

Function called when the Promise is settled.

返回值

返回 Promise whose finally handler is set to the specified function, onFinally .

描述

finally() method can be useful if you want to do some processing or cleanup once the promise is settled, regardless of its outcome.

finally() method is very similar to calling .then(onFinally, onFinally) however there are a couple of differences:

• When creating a function inline, you can pass it once, instead of being forced to either declare it twice, or create a variable for it
• A finally callback will not receive any argument, since there's no reliable means of determining if the promise was fulfilled or rejected. This use case is for precisely when you do not care about the rejection reason, or the fulfillment value, and so there's no need to provide it. So for example:
  • 不像 Promise.resolve(2).then(() => {}, () => {}) (which will be resolved with undefined ), Promise.resolve(2).finally(() => {}) will be resolved with 2 .
  • Similarly, unlike Promise.reject(3).then(() => {}, () => {}) (which will be fulfilled with undefined ), Promise.reject(3).finally(() => {}) will be rejected with 3 .

注意： A throw (or returning a rejected promise) in the finally callback will reject the new promise with the rejection reason specified when calling throw .

范例

Using finally

let isLoading = true;
fetch(myRequest).then(function(response) {
    var contentType = response.headers.get("content-type");
    if(contentType && contentType.includes("application/json")) {
      return response.json();
    }
    throw new TypeError("Oops, we haven't got JSON!");
  })
  .then(function(json) { /* process your JSON further */ })
  .catch(function(error) { console.error(error); /* this line can also throw, e.g. when console = {} */ })
  .finally(function() { isLoading = false; });
					

Please do not add polyfills on MDN pages. For more details, refer to: https://discourse.mozilla.org/t/mdn-rfc-001-mdn-wiki-pages-shouldnt-be-a-distributor-of-polyfills/24500

规范

规范
ECMAScript (ECMA-262) The definition of 'Promise.prototype.finally' in that specification.

浏览器兼容性

To contribute to this compatibility data, please write a pull request against this repository: https://github.com/mdn/browser-compat-data .

更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
finally()	Chrome 63	Edge 18	Firefox 58	IE No	Opera 50	Safari 11.1	WebView Android 63	Chrome Android 63	Firefox Android 58	Opera Android 46	Safari iOS 11.3	Samsung Internet Android 8.0	nodejs 10.0.0

图例

完整支持

完整支持

不支持

不支持

另请参阅

• Promise
• Promise.prototype.then()
• Promise.prototype.catch()

元数据

• 最后修改： May 7, 2020

相关话题

1. 标准内置对象
2. Promise
3. 方法
   1. Promise.all()
   2. Promise.allSettled()
   3. Promise.any()
   4. Promise.prototype.catch()
   5. Promise.prototype.finally()
   6. Promise.prototype.then()
   7. Promise.race()
   8. Promise.reject()
   9. Promise.resolve()
4. 继承：
5. Function
6. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
7. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
8. Object
9. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
10. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()