[英]Return from callback function in Javascript
How do I get the return value from inside a value of node.js/javascript callback?如何从 node.js/javascript 回调的值中获取返回值?
function get_logs(){
User_Log.findOne({userId:req.user._id}, function(err, userlogs){
if(err) throw err;
if(userlogs){
// logs = userlogs.logs;
return "hello there is a logs";
} else {
return "there is no logs yet..."
}
})
}
var logs = get_logs();
console.log(logs);
You can't return the result from a function whose execution is asynchronous. 您不能从执行异步的函数返回结果。
The simplest solution is to pass a callback : 最简单的解决方案是传递回调:
function get_logs(cb){
User_Log.findOne({userId:req.user._id}, function(err, userlogs){
if(err) throw err;
if(userlogs){
// logs = userlogs.logs;
cb("hello there is a logs");
} else {
cb("there is no logs yet...)"
}
})
}
get_logs(function(logs){
console.log(logs);
});
You can't. 你不能 You should instead pass another callback to your function.
您应该改为将另一个回调传递给函数。 Something like this:
像这样:
function get_logs(callback){
User_Log.findOne({userId:req.user._id}, function(err, userlogs){
if(err) throw err;
if(userlogs){
callback("hello there is a logs");
} else {
callback("there is no logs yet...");
}
})
}
get_logs(function(arg1) {
console.log(arg1);
});
function get_logs(callback) {
User_Log.findOne({
userId: req.user._id
}, function (err, userlogs) {
if (err) throw err;
if (userlogs) {
// logs = userlogs.logs;
callback("hello there is a logs");
} else {
callback("there is no logs yet...");
}
})
}
get_logs(function (data) {
console.log(data);
});
Uses callbacks... 使用回调...
In node.js almost all the callbacks run after the function returns , so you can do something like this 在node.js中,几乎所有的回调都在函数返回之后运行,因此您可以执行以下操作
function get_logs(){
User_Log.findOne({userId:req.user._id}, function(err, userlogs){
if(err) throw err;
if(userlogs){
// logs = userlogs.logs;
do_something(logs)
} else {
console.log('No logs')
}
})
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.