javascript - 在 Javascript 中返回未定义的函数

Question

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

var rob = new people("robert jr", 41);
var sam = new people("sam davies", 25);

function isOlderThan(age) {
  if(rob.age > sam.age) 
    return true;
  else return false;
}

我试着用这个 sam.isOlderThan(rob) 运行它；

但它不起作用。我对此有点陌生，有什么帮助吗？

Answer 1

//  If you want to be able to call this as sam.isOlderThan()
//  you need to use a prototype to add that function to the persons
//  so they all have that function bound to them.
function person (name, age) {
  this.name = name;
  this.age = age;
}
person.prototype.isOlderThan = function( other_person ) {
  return this.age > other_person.age;
};
var rob = new person("robert jr", 41);
var sam = new person("sam davies", 25);

console.log( sam.isOlderThan( rob ) );
console.log( rob.isOlderThan( sam ) );