Await,ASync原理最暴力解读

Await和Async其实就是promise的封装,使用编译技术自动将Await/Async转化为promise,为了更好的理解Await,Async是什么?我们使用转换工具来分析
 async/await转换工具安装
 $ sudo npm  install  babel - plugin -async- to -promises -g
 $  babel  -- plugins  async- to -promises async_test. js
 
function getConstant () {
return 1
}

async function getAsyncConstant () {
return 1
}

async function getPromise () {
return new Promise((resolved, rejected)=> {
resolved( 1 )
});
}

async function test () {
a = 2
c = 1
await getConstant ();
d = 3
await getPromise ();
d = 4
await getAsyncConstant ();
return 2
}
function getConstant () {
return 1 ;
}

function getAsyncConstant () {
return Promise. resolve (). then ( function () {
return 1 ;
});
}

function getPromise () {
return Promise. resolve (). then ( function () {
return new Promise((resolved, rejected) => {
resolved( 1 );
});
});
}

function test () {
return Promise. resolve (). then ( function () {
a = 2 ;
c = 1 ;
return getConstant ();
}). then ( function () {
d = 3 ;
return getPromise ();
}). then ( function () {
d = 4 ;
return getAsyncConstant ();
}). then ( function () {
return 2 ;
});
}
从上可知, 所有带async function 的都会主动生成Promise, await会主动生成then

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