说我有一个使用Socket.IO的nodeJS服务器。一个监听器是异步的,就像这样:
let aHugeArray = new Array(50000000);
// ... fill the array with data...
// print the array asynchronously:
socket.on('print-array', async () => {
let isFinished = await printArray();
});
// remove an item from the array:
socket.on('remove-from-array', (item : any) => {
let index = aHugeArray.indexOf(item);
aHugeArray.splice(index, 1);
});
private async printArray() : Promise<boolean> {
for (let i = 0; i < aHugeArray.length; i++) {
console.log(aHugeArray[i]);
}
return true;
}
假设我先调用print-array
,然后立即调用remove-from-array
(它将在print-array
完成遍历整个数组之前执行。在这种情况下会发生什么情况?remove-from-array
aHugeArray
还是被操纵,可能在其余print-array
循环迭代中导致奇怪的结果?
答案 0 :(得分:2)
print-array函数不是异步的,因此除非您拥有大量内存,否则在等待运行remove-from-array时抓住它的内容并记录它们不会明显阻塞线程
如果您需要先完成某项功能,然后对它进行承诺
const IMightTakeSomeTime = new Promise ((resolve, fail) => {
setTimeout(() => {
resolve(console.log('i am finished'))
}, 3000);
})
IMightTakeSomeTime.then(() =>
console.log('Now its my time to shine')
)
或者如果您想花哨的话可以使用async / await
const IMightTakeSomeTime = new Promise ((resolve, fail) => {
setTimeout(() => {
resolve(console.log('i am finished'))
}, 3000);
})
const run = async () => {
await IMightTakeSomeTime
console.log('Now its my time to shine')
}
run()
如果您想查看一个众所周知的非异步线程阻塞功能,请查看Node.js fs库的同步版本,该库中有一些不需要等待的“同步”版本
https://nodejs.org/api/fs.html#fs_fs_readfilesync_path_options