How to create a method/function for array/object

Question

This is my first question, so please be gentle.

I'm trying to create an array of objects, where the object includes a method/function to retrieve data.

So eventually I don't want to use getFirstName(arrayName, arrayNumber), but instead use something like

aliens[x].getFirstName;

or

persons.first.getFirstName;

If it's not possible in Javascript, or possible in this manner, please suggest the next best thing.

var persons = [

{
    firstname : "John",
    lastname  : "Doe",
    age       : 50,
    eyecolor  : "blue",
},

{
    firstname : "Jane",
    lastname  : "Siyabonga",
    age       : 39,
    eyecolor  : "brown",
},
]

var aliens = [

{
    firstname : "Bob",
    lastname  : "the Alien",
    age       : 350,
    eyecolor  : "yellow",
},

{
    firstname : "xblanque",
    lastname  : "the Predator",
    age       : 19,
    eyecolor  : "red",
},

]

function getFirstName(arrayName, arrayNumber)
{
    var x = arrayName[arrayNumber].firstname;
    return x;
}

Array.prototype.getLastName=function()
{
    var x = this.lastname;
    return x;
}

See this answer that deals with the same question.

isaach1000
– isaach1000

2013-05-06 13:48:07 +00:00
Commented May 6, 2013 at 13:48 — isaach1000
– isaach1000, Commented May 6, 2013 at 13:48

jAndy · Accepted Answer · 2013-05-06 13:46:23Z

5

ECMAscript supports getter and setter methods. In any ES5 compatible implementation, we can use it like

var obj = {
    foo: 42,
    bar: 32,
    get getFoo() {
        return this.foo;
    },
    get sum() {
        return this.foo + this.bar;
    }
};

now we can acces it like

obj.getFoo;  // 42
obj.sum;     // 74

Another way to create those is ES5's Object.defineProperty. For instance:

Object.defineProperty(obj, 'getBar', {
    get: function() {
        return this.bar;
    }
});

answered May 6, 2013 at 13:46

jAndy

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3 Comments

coma Over a year ago

getters and setters are great!

MisterBrownZA Over a year ago

I have never heard of ECMAscript, as I am a self-taught programmer. I'm going to google it now, but I'd like to know if it's default in all/most browsers ? IF I were to use this, would it work ?

jAndy Over a year ago

@MisterBrownZA: ECMAscript and JavaScript are one of a kind. For the compatibility, it will work in all latest browsers 100%. It will also work in older versions for most browsers. Only legacy browsers like IE 6-7 might have a problem with this syntax.

Tasso Evangelista · Accepted Answer · 2013-05-06 13:54:23Z

1

aliens[x].firstname; works fine. But, as @jAndy suggested, you can make use of getters and setters, like any OOP language.

function Alien( firstname, lastname, age, eyecolor) { // constructor

    // ...

    this.getFirstName = function() {
        return firstname;
    };
}

var aliens = [
    new Alien("Bob", "the Alien", 350, "yellow"),
    new Alien("xblanque", "the Predator", 19, "red")
];

console.log(aliens[0].getFirstName()); // will output "Bob"

Also, beware Array.prototype manipulation: you are adding getLastName method to any array present in your code.

answered May 6, 2013 at 13:54

Tasso Evangelista

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2 Comments

MisterBrownZA Over a year ago

That's what I was afraid of, and thought that it was wrong. Just to confirm, when you say new Alien("","","","") are you calling the function from above, or are you creating an object?

Tasso Evangelista Over a year ago

@MisterBrownZA Creating a object, because I'm using Alien as constructor function. You must understand that in Javascript everything behaves like a object. About functions, you must pay attention to the concept of "closure". When a function is called with operator new, a object is allocated in closure of function and its reference is this. Also, new ensures that this will be returned.

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