Question

我在这样的app.js文件中有一个数组：

   var data = [
                {id:1, firstName: 'John', lastName: 'Smith'},
                {id:2, firstName: 'Jane', lastName: 'Smith'},
                {id:3, firstName: 'John', lastName: 'Doe'}
              ];

现在，我正在使用Node.js并尝试在module.js文件中创建函数调用addEmployee（）。 addEmplyee（）只需要两个argurments，即添加的firstName和lastName。应使用underscore.js将id值计算为比当前最大id多一个。这是我在module.js文件中的代码，但它不起作用。

var _ = require('underscore');
module.exports = {
    addEmployee: function (firstName, lastName) {

        function Person(id, firstName, lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
            this.id = function (data) {
                var id = _.max(data, function (data) {
                    return data.id;
                });
                return id.id + 1;
            }
            var person = new Person(id, firstName, lastName);
            data.push(person);
            return data;

        }
    }
}

有人可以帮忙吗？非常感谢你！

Answer 1

试试这个：

var _ = require('underscore');
module.exports = {
    addEmployee: function (firstName, lastName) {

        function Person(id, firstName, lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
            this.id = (function (data) {
                var id = _.max(data, function (data) {
                    return data.id;
                });
                return id.id + 1;
            })();    //IIFE to invoke function immidiately and thus assign value to id
            data.push({id: this.id,firstName: this.firstName,lastName: this.lastName});
            return data;

        }
    }
}

Answer 2

应该是这样的：

var _ = require('underscore');
// import data

module.exports = {
    addEmployee: function (firstName, lastName) {
        // remove id
        function Person(firstName, lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
            this.id = (function (data) {
                var id = _.max(data, function (data) {
                    return data.id;
                });
                return id.id + 1;
            })();    
        }

        // put OUTSIDE - dont need id here
        var person = new Person(firstName, lastName);
        data.push(person);
        return data;
    }
}

Answer 3

首先，你无论如何都不会调用这个内部函数/ contstructor，因此它不会被添加到数组中。其次，不要在函数内定义Person（它将在每次调用时定义为新事物 - 每个新Person都是新类型）。第三件事是，如果你调用你的代码，它会导致无限循环（在构造函数中调用new on self会在下一个新实例中执行相同操作，依此类推）。另外，您在哪里定义/导入数据？

var _ = require('underscore');

// probably it'd be even better to move this to separate module
function Person(id, firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.id = id;
};

module.exports = {
    addEmployee: function (firstName, lastName) {
        data.push(new Person((_.max(data, function (data) {
            return data.id;
        }) + 1), firstName, lastName));
    }
}

我还建议使用lodash代替undescore（直接替换，但写得更好）。

如果您只需要保留数据{ id, firstName, lastName }的对象，则不需要新类型Person：

module.exports = {
    addEmployee: function (firstName, lastName) {
        var id = (_.max(data, function (data) {
            return data.id;
        }) + 1);
        data.push({ id: id, firstName: firstName, lastName: lastName });
    }
}

如果使用节点6.X或4.X +（不确定es6表示法是否适用于所有4.X，肯定4.4+将使用'use strict';，它可能更短：

'use strict';

var _ = require('underscore');

module.exports = {
    addEmployee: function (firstName, lastName) {
        var id = (_.max(data, function (data) {
            return data.id;
        }) + 1);
        data.push({ id, firstName, lastName });
    }
}

最后，我建议不要改变数据（副作用主要是坏的） - 我将其转换为类似的东西（假设可以执行es6的节点）：

'use strict';

const _ = require('underscore');

module.exports = {
    // note that data comes as input
    addEmployee: function (data, firstName, lastName) {
        // obtain next id
        const id = (_.max(data, function (data) {
            return data.id;
        }) + 1);
        // return new data (old data + new object, but without mutation of initial object)
        return [...data, { id, firstName, lastName }];
    }
}

如何使用javascript将对象添加到数组中？

3 个答案: