Node. js loop traps and node. js loop traps

Node. js loop traps and node. js loop traps

The asynchronous mechanism of Node. js is implemented by events and callback functions. It may feel like a violation of the Conventions at the beginning, but it will be very easy to get used to later.

However, there are actually many traps hidden in this process. A very easy problem is to return to the loop callback function.

Eq:

Var fs = require ('fs'); var files00000000'a.txt', 'B .txt', 'c.txt']; for (var I = 0; I <files. length; I ++) {fs. readFile (file [I], 'utf-8', function (err, contents) {console. log (files); console. log (I); console. log (files [I]) ;}}

The actual running result is as follows:

Comment '] 3 undefined

The solution is as follows:

Var fs = require ('fs'); var files?}'a.txt', 'B .txt', 'c.txt']; files. forEach (function (filename) {fs. readFile (filename, 'utf-8', function (err, contents) {console. log (filename + ":" + contents );})})