node js event loop monitoring

first, let's explain what the event loop is:As far as we know, the browser's JS is single-threaded, that is, at the same time, at most only one code snippet is executing, but the browser can handle the asynchronous request very well, then exactly why is it? Let's take a look at a picture (this picture comes from http://www.zcfy.cc/article/

: var asnyc = function (callback) {Process.nexttick (callback);};After the call to Async (), the callback is stored until the next event loop (tick) is removed for execution. An attempt to try/catch an asynchronous method can only catch exceptions that occur within the secondary event loop. The exception thrown when t

Event polling (reference)Event polling is the core content of node. A system (or a program) must contain at least one large loop structure (what I call a "pump"), which is a prerequisite for sustaining the system's continuous operation. The same structure is included in Nodejs, which we call "

On JS event Monitoring1, before talking about event monitoring, first to understand what is the JS event?We all know that JS is a dynamic data type of language, you can make us in the o

In-depth understanding of Node. js event loops and callback functions this article describes in detail the Node. js event loops and Node. js

threads, concurrency problems often make you stuck in the box ). In node. js, you do not need to worry about the occurrence of your code on the backend. You only need to use the callback when you perform I/O operations. You will be guaranteed that your code will not be interrupted, and I/O operations will not block other requests (because there is no overhead required by those threads/processes, for exampl

Introduction and Materials Http://nodejs.org/api/events.html Http://www.infoq.com/cn/articles/tyq-nodejs-event Events is the most important module of node. js. The events module provides only one events. EventEmitter object. The core of EventEmitter is event launch and event

places call it the main thread). In fact, JavaScript's browser environment is not the same as the way we write JavaScript code, and many tasks of parallel processing, it is necessary to multi-threading, for example:For example, the single thread in node. JS is referring to this primary thread. This main thread has a looping structure. Keep the whole program running (the code you wrote).

, found that the micro-task queue is empty, then go to the macro-benevolence queue to find, found that we have just put in the settimeout callback function, then take out this task to execute, so immediately after the output 1Console.log (4);Copy the code to see the above explanation, we are not all understand, is not straight call simple ~So let's take a look at the event execution ring in the node environ

outputbtn。 6, event agent because the event will propagate up to the parent node in the bubbling phase, so the listener function of the node can be defined on the parent node, and the listener function of the parent node handles

, data) {if (err) {Console.log (Err.stack);Return}Console.log (Data.tostring ());});Console.log ("program execution Complete");The above program Fs.readfile () is an asynchronous function used to read the file. If an error occurs during the reading of the file, the error Err object will output an error message.If no error occurs, ReadFile skips the output of the Err object, and the contents of the file are output through the callback function.Execute the above code and execute the result as foll

request to another. In an I/O call, the code saves the callback function and returns control to the runtime environment of node. js. The callback function is called when the data is available.Of course, in the background, there are threads and processes for database access and execution processes. However, this does not expose the code, so you do not need to worry about I/O operations, for example, the dat

In JS, it is a common problem to use loops to bind events to elements of a pair of element queues.People who usually enter the wrong way will write code like this: (assuming that the element queue is O, jquery is used by default)Error methodvar o =$ ('. Blockhead '); for (var i=0; iOf course, in this case, you will find that each element clicked to run, the I value displayed is o.length-1;Because the function of J