Using q. js to implement promise of common node APIs

Here we will look at how to use q. js to implement node api promise.

1. Everything starts with install

Npm install q

2. Standard node style api promise method

1. Use Q. nfcall

Compared with Q. fcall, Q. nfcall is the node's Q. fcall.

 

The code is as follows:	Copy code
Var FS = require ('Fs '), Q = require ('Q '), Colors = require ('Colors '), File = 'example.txt '; Var fsReadFile = Q. nfcall (FS. readFile, file, encoding ); FsReadFile. then (function (result ){ Console. log ("invoke in nfcall" + file). red ); Console. log (result. green ); }, Function (error ){ Console. log ("invoke in nfcall". red ); Console. log (error. toString (). red ); } );

2 Use Q. denodeify

The code is as follows:	Copy code
Var fsReadFile_denodeify = Q. denodeify (FS. readFile );   FsReadFile_denodeify (file, encoding). then (function (result ){ Console. log ("invoke in denodeify". red ); Console. log (result. green) }, Function (error ){ Console. log ("invoke in denodeify". red ); Console. log (error. toString (). red ); } );

3. Use Q. deferd

The code is as follows:

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Var fsReadFile_deferd = function (file, encoding ){ Var deferred = Q. defer (); FS. readFile (file, encoding, function (error, result ){ If (error ){ Deferred. reject (error. toString (). red );     } Deferred. resolve (result ); });   Return deferred. promise; };   FsReadFile_deferd (file). then (function (result ){ Console. log ("invoke in deferd". red ); Console. log (result. toString (). green ); }, Function (error ){ Console. log ("invoke in deferd". red ); Console. log (error. toString (). red ); } );

4. Use makeNodeResolver ()

The code is as follows:

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Var fsReadFile_makeNodeResolver = function (file, encoding ){ Var deferred = Q. defer (); FS. readFile (file, encoding, deferred. makeNodeResolver ()); Return deferred. promise; };   FsReadFile_makeNodeResolver (file, encoding). then (function (result ){ Console. log ("invoke in makeNodeResolver". red ); Console. log (result. green ); }, Function (error ){ Console. log (error. toString (). red ); });