我无法准确理解process.nextTick如何做到这一点.我以为我理解了,但我似乎无法复制我觉得这应该如何工作:
- var handler = function(req,res) {
- res.writeHead(200,{'Content-type' : 'text/html'});
- foo(function() {
- console.log("bar");
- });
- console.log("received");
- res.end("Hello,world!");
- }
- function foo(callback) {
- var i = 0;
- while(i<1000000000) i++;
- process.nextTick(callback);
- }
- require('http').createServer(handler).listen(3000);
当foo循环时,我会发送几个请求,假设处理程序将在foo后面排队几次,只有当foo完成后才会将回调排入队列.
如果我对这是如何工作正确的,我认为结果将如下所示:
- received
- received
- received
- received
- bar
- bar
- bar
- bar
但它没有,它只是顺序的:
- received
- bar
- received
- bar
- received
- bar
- received
- bar
我看到foo在执行回调之前正在返回,这是预期的,但似乎回调是NEXT在行,而不是在队列的末尾,在所有请求进入后面.这是否有效?也许我只是不明白节点中的事件队列是如何工作的.请不要指向我here.谢谢.
解决方法
process.nextTick将回调放在将要执行的下一个tick上,而不是在tick队列的末尾.
Node.js doc(http://nodejs.org/api/process.html#process_process_nexttick_callback)说:
“它通常在任何其他I / O事件发生之前运行,但也有一些例外情况.”
setTimeout(callback,0)可能更像你描述的那样工作.