是否访问作用域之外的变量？nodejs

Question

function art(dataToArt){
  var figlet = require('figlet');
var result;
figlet(dataToArt, function(err, data) {
    if (err) {
        console.log('Something went wrong...');
        console.dir(err);
        return;
    }
    var result = data;
});
return result;
}

test = art('Hello World');

console.log(test);

运行此命令会产生“未定义”。如何访问function figlet对function figlet外部定义的变量result所做的更改。

Answer 1

这是异步代码。它不能返回。它必须有回调，并在作业完成后响应。

var figlet = require('figlet');

function art(dataToArt, callback)
{ 
    figlet(dataToArt, function(err, data) { 
        if (err) { 
            console.log('Something went wrong...'); 
            console.dir(err); 
            return callback(''); 
        } 

        callback(data);
    }); 
} 


art('Hello World', function (data){
    console.log(data);
    // also You can do operations here.
    // for example can save to db or send to somewhere.
});

Answer 2

@num8er的answer是完全正确的。

我个人喜欢使用promises

var figlet = require('figlet');

function art(dataToArt) {
    return new Promise(function(fullfil, reject) {
        figlet(dataToArt, function(err, data) {
            if (err) {
                reject(err);
            } else {
                fullfil(data);
            }
        });
    });
}

art('Hello World').then(function(result) {
    console.log(result);
});