封装异步 API （获取一个函数中异步操作的结果）

function fun(callback) {
    setTimeout(function () {
        var data = 1;
        callback(data);
    })
}

fun(function (data) {
    console.log(data);
})

exports.find = function (callback) {

    fs.readFile(‘./db.json‘, function (err, data) {
        if (err) {
            return callback(err);
        }
        callback(null, JSON.parse(data).students);
    });
};

var students = require(‘./students‘)

router.get(‘/students‘, function(req, res) {
    students.find(function (err, data) {
        res.render(‘index.html‘, data)
    })
})

{
    "students" :[
        {"id": 1, "name": "小白", "xuehao": 201561361351, "gender": 1, "core": 88},
        {"id": 2, "name": "小黑", "xuehao": 201561361352, "gender": 0, "core": 85},
        {"id": 3, "name": "小绿", "xuehao": 201561361353, "gender": 0, "core": 88},
        {"id": 4, "name": "小红", "xuehao": 201561361354, "gender": 1, "core": 95}
    ]
}