问题描述
你好,我有以下代码:
function updateData(){
return firebase.database().ref(varurl3).child('UserCount/count').once('value').then(function(snapshot) {
var username = snapshot.val();
var username2 = username+1;
return firebase.database().ref(varurl3).child('Users').child(username2).child('User').once('value').then(function(snapshot) {
var username3 = snapshot.val();
if(username3!= null){
//Here i want to stop my function for 2 seconds
}
});
});
}
timeupdater = setInterval(updateData,100);
当它进入if循环时,我想暂停我的函数。我尝试过睡眠,但该功能始终继续运行异步。就我而言,有没有一种方法可以将函数暂停2秒钟,以使timupdater不会在循环底部再次调用它?我将不胜感激。
解决方法
由于Firebase已经返回了承诺,因此请一路使用承诺。使用async
和await
可以简化为:
// Utility function to return a promise that resolves after a given delay
const delay = ms => new Promise(resolve => setTimeout(resolve,ms));
async function updateData(){
let ref = firebase.database().ref(varurl3);
let snapshot = await ref.child('UserCount/count').once('value');
var username = snapshot.val();
var username2 = username+1;
snapshot = await ref.child('Users').child(username2).child('User').once('value');
var username3 = snapshot.val();
// resolve a promise after 2 seconds
if (username3 != null) await delay(2000);
}
(async function looper() {
while (true) { // forever
await updateData();
await delay(100); // this was the setInterval delay
}
})(); // execute looper