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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

Promise.resolve() method returns a Promise object that is resolved with a given value. If the value is a promise, that promise is returned; if the value is a thenable (i.e. has a "then" method ), the returned promise will "follow" that thenable, adopting its eventual state; otherwise the returned promise will be fulfilled with the value. This function flattens nested layers of promise-like objects (e.g. a promise that resolves to a promise that resolves to something) into a single layer.

句法

Promise.resolve(value);
					

参数

value

Argument to be resolved by this Promise . Can also be a Promise or a thenable to resolve.

返回值

A Promise that is resolved with the given value, or the promise passed as value, if the value was a promise object.

描述

静态 Promise.resolve function returns a Promise that is resolved.

范例

Using the static Promise.resolve method

Promise.resolve('Success').then(function(value) {
  console.log(value); // "Success"
}, function(value) {
  // not called
});
					

Resolving an array

var p = Promise.resolve([1,2,3]);
p.then(function(v) {
  console.log(v[0]); // 1
});
					

Resolving another Promise

var original = Promise.resolve(33);
var cast = Promise.resolve(original);
cast.then(function(value) {
  console.log('value: ' + value);
});
console.log('original === cast ? ' + (original === cast));
// logs, in order:
// original === cast ? true
// value: 33
					

The inverted order of the logs is due to the fact that the then handlers are called asynchronously. See how then works here .

Resolving thenables and throwing Errors

// Resolving a thenable object
var p1 = Promise.resolve({
  then: function(onFulfill, onReject) { onFulfill('fulfilled!'); }
});
console.log(p1 instanceof Promise) // true, object casted to a Promise
p1.then(function(v) {
    console.log(v); // "fulfilled!"
  }, function(e) {
    // not called
});
// Thenable throws before callback
// Promise rejects
var thenable = { then: function(resolve) {
  throw new TypeError('Throwing');
  resolve('Resolving');
}};
var p2 = Promise.resolve(thenable);
p2.then(function(v) {
  // not called
}, function(e) {
  console.error(e); // TypeError: Throwing
});
// Thenable throws after callback
// Promise resolves
var thenable = { then: function(resolve) {
  resolve('Resolving');
  throw new TypeError('Throwing');
}};
var p3 = Promise.resolve(thenable);
p3.then(function(v) {
  console.log(v); // "Resolving"
}, function(e) {
  // not called
});
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Promise.resolve' 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
resolve()	Chrome 32	Edge 12	Firefox 29	IE No	Opera 19	Safari 8	WebView Android 4.4.3	Chrome Android 32	Firefox Android 29	Opera Android 19	Safari iOS 8	Samsung Internet Android 2.0	nodejs 0.12

图例

完整支持

完整支持

不支持

不支持

另请参阅

• Promise

元数据

• 最后修改： 2020 年 1 月 22 日

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()