使用回调内部循环修改回调外部变量的值

Question

我是Nodejs的新手，我面临着一个问题:修改回调外部变量的值与循环内的回调。

我正在编写在线判断项目，这是我的功能来检查一个程序的输出与数据库的答案。我创建了结果对象来存储正确的测试用例的数量。

function compareResult(fileName, problem, timeLimit, callback) {
const cp = require('child_process');
const exePath = 'submit\' + fileName + '.exe';
const child = cp.spawn(exePath, ['--from=markdown', '--to=html'], {timeout: timeLimit});
MongoClient.connect(uri, function(err, db) {
if (err) throw err;
var dbo = db.db(dbName);
var query = { id_problem: problem, is_eg: "false" };
var proj = { projection: {input: 1, output: 1} };
dbo.collection("sample").find(query, proj).toArray(function(err, arr) {
if (err) throw err;
if (arr != null) {
var result = {
correct: 0,
total: arr.length
};
for (const json of arr) {
const answer = json['output'];
child.stdin.write(json['input']);
child.stdout.on('data', function(data) {
if (data == answer) { 
result.correct += 1; // I want to modify result object here.
}
});
child.stdin.end();
};
console.log(result);
callback(result);
}
});
});

我想在那个地方修改结果对象。我该怎么做呢?

Answer 1

function compareResult(fileName, problem, timeLimit, callback) {
const cp = require('child_process');
const exePath = 'submit\' + fileName + '.exe';
const child = cp.spawn(exePath, ['--from=markdown', '--to=html'], {timeout: timeLimit});
MongoClient.connect(uri, function(err, db) {
if (err) throw err;
var dbo = db.db(dbName);
var query = { id_problem: problem, is_eg: "false" };
var proj = { projection: {input: 1, output: 1} };
dbo.collection("sample").find(query, proj).toArray(function(err, arr) {
if (err) throw err;
if (arr != null) {
var result = {
correct: 0,
total: arr.length
};
for (const json of arr) {
const answer = json['output'];
child.stdin.write(json['input']);
child.stdout.on('data', function(data) {
if (data == answer) { 
result.correct += 1; 
}
// Decrement total here to track how many 'data' events have been emitted
result.total--; 
if (result.total === 0) {
// All 'data' events have been emitted, so call the callback function
callback(result);
}
});
child.stdin.end();
};
}
});
});
}