Promise.resolve(value)
方法返回一个以给定值解析后的Promise
对象。但如果这个值是个thenable(即带有then方法),返回的promise会“跟随”这个thenable的对象,采用它的最终状态(指resolved/rejected/pending/settled);如果传入的value本身就是promise对象,则该对象作为Promise.resolve方法的返回值返回;否则以该值为成功状态返回promise对象。The source for this interactive demo is stored in a GitHub repository. If you'd like to contribute to the interactive demo project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
Promise.resolve(value);
Promise.resolve(promise);
Promise.resolve(thenable);
将被Promise
对象解析的参数。也可以是一个Promise
对象,或者是一个thenable。
返回一个解析过带着给定值的Promise
对象,如果返回值是一个promise对象,则直接返回这个Promise对象。
静态方法 Promise.resolve
返回一个解析过的Promise
对象.
Promise.resolve
Promise.resolve("Success").then(function(value) {
console.log(value); // "Success"
}, function(value) {
// 不会被调用
});
var p = Promise.resolve([1,2,3]);
p.then(function(v) {
console.log(v[0]); // 1
});
var original = Promise.resolve('我在第二行');
var cast = Promise.resolve(original);
cast.then(function(value) {
console.log('value: ' + value);
});
console.log('original === cast ? ' + (original === cast));
/*
* 打印顺序如下,这里有一个同步异步先后执行的区别
* original === cast ? true
* value: 我在第二行
*/
// Resolve一个thenable对象
var p1 = Promise.resolve({
then: function(onFulfill, onReject) { onFulfill("fulfilled!"); }
});
console.log(p1 instanceof Promise) // true, 这是一个Promise对象
p1.then(function(v) {
console.log(v); // 输出"fulfilled!"
}, function(e) {
// 不会被调用
});
// Thenable在callback之前抛出异常
// Promise rejects
var thenable = { then: function(resolve) {
throw new TypeError("Throwing");
resolve("Resolving");
}};
var p2 = Promise.resolve(thenable);
p2.then(function(v) {
// 不会被调用
}, function(e) {
console.log(e); // TypeError: Throwing
});
// Thenable在callback之后抛出异常
// 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); // 输出"Resolving"
}, function(e) {
// 不会被调用
});
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) Promise.resolve |
Standard | ECMA标准中的首次定义 |
ECMAScript Latest Draft (ECMA-262) Promise.resolve |
Standard |
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
resolve | Chrome Full support 32 | Edge Full support 12 | Firefox Full support 29 | IE No support No | Opera Full support 19 | Safari Full support 8 | WebView Android Full support 4.4.3 | Chrome Android Full support 32 | Edge Mobile Full support Yes | Firefox Android Full support 29 | Opera Android Full support Yes | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |