Cyclic traps in the Nodejs

The asynchronous mechanism of Node. JS is implemented by events and callback functions, which may feel like a violation of the routine, but the habit will find it very easy to get Started.

There are, however, many pitfalls in This. A very easy problem to encounter is to go back to the callback function of the Loop.

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 execution are as Follows:

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

The workaround 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);    })})

Cyclic traps in the Nodejs