128 lines
1.5 KiB
Markdown
128 lines
1.5 KiB
Markdown
#promise
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## 填空
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下面的打印结果是什么
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```
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const promise = new Promise((resolve, reject) => {
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console.log(1)
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resolve()
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console.log(2)
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})
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promise.then(() => {
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console.log(3)
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})
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console.log(4)
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```
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答案 1 2 4 3
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下面打印结果是什么
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```
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const promise = new Promise((resolve, reject) => {
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//resolve('success1')
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resolve('success2')
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reject('error)
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})
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promise
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.then((res) => {
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console.log('then: ', res)
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})
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.catch((err) => {
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console.log('catch: ', err)
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})
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```
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答案 then: success1
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下面打印结果是什么
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```
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Promise.resolve(1)
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.then((res) => {
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console.log(res)
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return 2
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})
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.catch((err) => {
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return 3
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})
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.then((res) => {
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console.log(res)
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})
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```
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答案 1 2
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下面打印结果是
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```
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let a = 1;
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const promise = new Promise((resolve, reject) => {
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setTimeout(() => {
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console.log('once')
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console.log(a)
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resolve(a++)
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}, 1000)
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})
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const start = Date.now()
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promise.then((res) => {
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console.log(res)
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})
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promise.then((res) => {
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console.log(res)
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})
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```
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答案
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once
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1
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1
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下面代码打印结果是
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```
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async function asyncFn() {
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return 'hello world';
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}
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console.log(asyncFn())
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```
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答案：
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Promise {<resolved>: "hello world"}
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下面代码打印结果是
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```
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async function asyncFn() {
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return 1;
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}
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asyncFn()
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.then(res => {
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console.log(res);
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})
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```
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答案 1
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下面写法是否正确
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```
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let a = new Promise((res)=>{
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console.log(1)
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res(1)
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})
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function name(){
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let a = await a;
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}
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```
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答案 错误
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