async ... await in the use of some attention problems using object Promise

May await an asynchronous with the expression (e.g., expression promise), may be followed by a regular expression (eg: console.log (123))

Example 1: If the immediately await a promise not resolve the object, the subsequent code will not be executed. Such as:

async function a(){
    // 如果await后是promise对象 
    await new Promise(resolve => {
        console.log(66666)
    })
    console.log(1)
}
a();
Promise.resolve().then(()=>{
    console.log(3)
})

operation result:

运行结果:
    66666
    3

Here we must note, console.log (1) will not be executed, because

async function a(){
    // 如果await紧跟一个普通表达式
    await console.log(1);
    console.log(2)
}

Equivalent to

async function a(){
    new Promise(resolve => {
        console.log(1)
    }).then(() => {
        console.log(2)
    })
}

Since there is no state Promise not resolved, it will not perform subsequent .then code.

Run process diagram:

Examples 2: Promise if the object await followed an already resolved the 

async function a(){
    // 如果await紧跟一个已经resolved的promise对象 
    await new Promise(resolve => {
        resolve();
        console.log(66666)
    })
    console.log(1)
}
a();
Promise.resolve().then(()=>{
    console.log(3)
})

operation result:

运行结果:
    66666
    1
    3

Run process diagram:

 

Example 3: After await followed by a regular expression

async function a(){
    // 如果await紧跟一个普通表达式
    await console.log(1);
    console.log(2)
}
a();
Promise.resolve().then(()=>{
    console.log(3)
})

operation result:

运行结果:
    1
    2
    3

Run process diagram:

Example 4: A more complex example

function c(){
    return new Promise((resolve)=>{
        console.log('开始了')
        resolve()
    }).then(()=> {
        console.log('c.......');
        return 65666
    }).then(res => {
        console.log(res);
        return '返回了一个值'
    })
}
async function a(){
    // 如果await后的表达式是一个promise对象 
    await c().then((res)=>{
        console.log('then....' + res)
    })
    console.log(1)
}
a();
console.log('同步代码')
Promise.resolve().then(()=>{
    console.log(3)
})

operation result:

    '开始了'
    '同步代码'
    'c.......'
    3
    65666
    'then....返回了一个值'
    1

Run process diagram:

Example 9: