Cyclic traps in the Nodejs

The asynchronous mechanism of node. JS is implemented by events and callback functions, and it may feel like a violation of the routine at first, but the habit will find it simple.

However, there are a lot of traps in this, a very easy problem is to return to the loop callback function.

eq

var fs=require (' FS '); var files=[' 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 results of the actual operation are as follows:

[' A.txt ', ' b.txt ', ' c.txt ']3undefined[' a.txt ', ' b.txt ', ' c.txt ']3undefined[' a.txt ', ' b.txt ', ' c.txt ']3undefined

Here's how to fix it:

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);    })})

Cyclic traps in the Nodejs