[英]How to pass variable to callback function?
I have a simple example: 我有一个简单的例子:
for ( i in dbs ) {
var db = dbs[i].split(':')
var port = dbs[i][0]
var host = dbs[i][0]
var client = redis.createClient( port, host )
tasks = [ [ "info" ] ]
client.multi(tasks).exec(function (err, replies ) {
console.log(port)
})
How to print corrent port for each client connect ? 如何为每个客户端连接打印相应的端口?
A simple way is to enclose the loop body in a self-invoking anonymous function: 一种简单的方法是将循环主体包含在一个自调用匿名函数中:
for (var i in dbs) {
(function(i) {
var db = dbs[i].split(":");
var host = db[0]; // Probably 'db[0]' instead of 'dbs[i][0]'.
var port = db[1]; // Probably 'db[1]' instead of 'dbs[i][0]'.
var client = redis.createClient(port, host);
tasks = [ [ "info" ] ];
client.multi(tasks).exec(function(err, replies) {
console.log(port);
});
})(i);
}
That way, the current value of port
is properly captured by the closure and will be available in the callback passed to exec()
. 这样,
port
的当前值将由闭包正确捕获,并将在传递给exec()
的回调中使用。
Note this answer assumes that dbs
is an object, not an array, even though you're using i
as the loop variable. 请注意,即使您将
i
用作循环变量,该答案也假定dbs
是一个对象,而不是数组。 If dbs
is an array, you should use an indexed loop instead: 如果
dbs
是一个数组,则应改用索引循环:
for (var i = 0; i < dbs.length; ++i) {
// ...
}
Because for... in
loops are not meant to iterate over arrays . 因为
for... in
循环并不意味着要在array上进行迭代 。
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