In node.js q.js is used to realize the promise of API

About what is the promise and promise to solve is what problem, please let us experience the callback asynchronous node coding solution, helping to set (link: http://wiki.commonjs.org/wiki/Promises/A) to see is defined at first sight, go here.

Here's how to implement the promise of the node API using q.js.

1. Everything starts with install

npm install q

Ii. Promising method of standard node style API

1. Use q.nfcall

Compared with q.fcall, q.nfcall is the q.fcall of node.

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.docodeify

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

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()

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);

});