[英]Are Promise.resolve and new Promise(resolve) interchangeable
I think Promise.resolve
and new Promise(resolve)
are interchangeable. 我认为
Promise.resolve
和new Promise(resolve)
是可以互换的。
Consider this: 考虑一下:
A. 一个。
new RSVP.Promise(function (resolve, reject) {
resolve();
}).then(function () {
return new RSVP.Promise(function (resolve) {
resolve("HI")
});
}).then(function (result) {
console.log(result);
});
B. B.
new RSVP.Promise(function (resolve, reject) {
resolve();
}).then(function () {
return RSVP.resolve("HI");
}).then(function (result) {
console.log(result);
});
Both print "HI" as I expected. 两者都按照我的预期打印“HI”。
So I think if I don't need to "reject" anything. 所以我想如果我不需要“拒绝”任何东西。 I can just write
RSVP.resolve();
我可以写
RSVP.resolve();
for simplicity. 为简单起见。
But consider this example: 但请考虑这个例子:
new RSVP.Promise(function (resolve, reject) {
resolve();
}).then(function () {
return new RSVP.Promise(function (resolve, reject) {
setTimeout(function () {
resolve("HI")
}, 3000);
});
}).then(function (result) {
console.log(result);
});
How can I use RSVP.resolve();
我怎样才能使用
RSVP.resolve();
to replace? 取代? I tried for example:
我试过例如:
new RSVP.Promise(function (resolve, reject) {
resolve();
}).then(function () {
return setTimeout(function () {
return new RSVP.resolve("HI");
}, 3000);
}).then(function (result) {
console.log(result);
});
This prints something else instead of "HI". 这打印出别的东西而不是“HI”。 So is it possible to use RSVP.resolve();
那么可以使用RSVP.resolve(); here?
这里? Are these two interchangeable?
这两个可以互换吗?
First and foremost 首先是最重要的
I think Promise.resolve and new Promise(resolve) are interchangeable.
我认为Promise.resolve和新的Promise(解决)是可以互换的。
Nope. 不。
Promise.resolve
will create a promise which is already resolved, whereas new Promise(resolve)
creates a promise which is neither resolved nor rejected. Promise.resolve
将创建一个已经解决的承诺,而new Promise(resolve)
创建一个既未解决也Promise.resolve
拒绝的承诺。
In the last example, 在最后一个例子中,
return setTimeout(function () {
return new RSVP.resolve("HI");
}, 3000);
means that, you are returning the result of setTimeout
function, not a promise object. 意味着,您将返回
setTimeout
函数的结果,而不是promise对象。 So, the current then
handler will return a resolved promise with the result of setTimeout
. 因此,目前的
then
处理程序将返回结果的解决承诺setTimeout
。 That is why you are seeing a weird object. 这就是为什么你看到一个奇怪的对象。
In your particular case, you want to introduce a delay before resolving the promise. 在您的特定情况下,您希望在解决承诺之前引入延迟。 It is not possible with
Promise.resolve
. Promise.resolve
是不可能的。 The penultimate method you have shown in the question, is the way to go. 您在问题中显示的倒数第二种方法是要走的路。
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