Question

我遇到了在javascript中向对象添加方法的问题。以下代码应返回一个数字，而是返回NaN。希望你能帮忙

function people(name, age){
    this.name = name;
    this.age = age;
    this.numYearsLeft = pension();
}

function pension(){
    numYears = 65 - this.age;
    return numYears;
}

var andrews = new people("Andrews Green", 28);

console.log(andrews.numYearsLeft);

Answer 1

您可以使用原型模型 - 使pension成为people的方法：

function people(name, age){
  this.name = name;
  this.age = age;
  this.numYearsLeft = this.pension();  // note the `this`
}

people.prototype.pension = function(){ // note the `prototype`
  var numYears = 65 - this.age;
  return numYears;
};

var andrews = new people("Andrews Green", 28);

console.log(andrews.numYearsLeft);     // 37

使用prototype您的pension方法将继承构造函数（people）属性（允许您使用this关键字进行引用）。
这样做的另一个好处是，在new people的每个pension实例化中，您都不会重新创建from multiprocessing import Process import datetime class foo: def fun1(): do sthn def fun2(): do sthn ob = foo() if __name__ == '__main__': p1 = Process(target = ob.fun1) p1.start() p2 = Process(target = ob.fun2) p2.start() endTime=datetime.datetime.now() print 'Program Ending time is: ', endTime方法的新实例/召回。

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Introduction_to_Object-Oriented_JavaScript

Answer 2

JavaScript适用于“功能范围”，所以简而言之，你的范围是错误的。您需要绑定“this”变量或使用prototype属性在people类上创建一个函数。

您可以将其定义为原型函数

people.prototype.pension = function() {
    numYears = 65 - this.age;
    return numYears;
}

Answer 3

如果在养老金中添加console.log（）行，您会看到this是窗口而不是人物对象。更改this的一种方法是使用call（）。

this.numYearsLeft = pension.call(this);

示例：

＆＃13;

function people(name, age) {
  this.name = name;
  this.age = age;
  this.numYearsLeft = pension.call(this);

}

function pension() {
  numYears = 65 - this.age;
  return numYears;
}

var andrews = new people("Andrews Green", 28);

console.log(andrews.numYearsLeft);

＆＃13;

其他选择是让它成为人物原型的一部分。

＆＃13;

function people(name, age) {
  this.name = name;
  this.age = age;
  this.numYearsLeft = this.pension();

}

people.prototype.pension = function () {
  numYears = 65 - this.age;
  return numYears;
}

var andrews = new people("Andrews Green", 28);

console.log(andrews.numYearsLeft);

＆＃13;

Answer 4

为了调用函数，你需要put（）。 console.log(andrews.numYearsLeft);应为console.log(andrews.numYearsLeft());

同样在

function pension(){
numYears = 65 - this.age;
return numYears;
}

this.age未定义，因此是NaN。

（编辑）也许试试：

function people(name, age){
    var that = this;
    this.name = name;
    this.age = age;
    this.numYearsLeft = function(){
        numYears = 65 - that.age;
        return numYears;
    };
}
var andrews = new people("Andrews Green", 28);
console.log(andrews.numYearsLeft());

向对象添加方法

4 个答案: