CODEWITHSUNDEEP
javascriptarraysobjectinitialization
PandaDeTapas
PandaDeTapas

Reputation: 516

Initiate objects from associative array

I want to use the init() method to initiate objects taken from an associative array by a for..in loop:

var person = {name: null, id: null}

person.init = function(name){
    this.name = name;
    this.id = "##" + this.name;
}

var pers1 = Object.create(person);
var pers2 = Object.create(person);

var personArray = {pers1: "John", pers2: "Alice"};

for (var i in personArray){
    console.log(i);
    console.log(personArray[i]);
    console.log(i.name);
    i.init(personArray[i]);
}

Output:

pers1
John       
undefined  // pers1.name
TypeError: i.init is not a function  //But not pers1.init() ?

Why can I call the .name attribute but not the .init() method? And more importantly, is there a way to call the methods of objects in an array?

I am a beginner at JS so I'm sorry if the code looks a bit weird.

Upvotes: 0

Views: 52

Answers (2)

T.J. Crowder
T.J. Crowder

Reputation: 1075159

Why can I call the .name attribute but not the .init() method?

In JavaScript, you can access non-existent properties on objects; when you do, you get back the value undefined. That's what you're doing: The values of the properties on personArray (which isn't an array) are strings, and don't have name or init properties. That's fine for accessing .name, because all you do is pass it to console.log, but you get an error for .init because you're trying to call undefined as a function.

The main issue is that your properties in the object (it's not an array) are not related in any way to your person function, and are not related in any way to your pers1 and pers2 objects.

If your goal is to start with an object with properties whose values are just names, and convert it into an object with objects using those names backed by the person object, you can do this:

var person = {name: null, id: null};

person.init = function(name){
    this.name = name;
    this.id = "##" + this.name;
};

var personMap = {pers1: "John", pers2: "Alice"};

var name;
for (var i in personMap) {
    name = personMap[i];
    personMap[i] = Object.create(person);
    personMap[i].init(name);
}

Upvotes: 1

Joe Fitter
Joe Fitter

Reputation: 1309

var personArray = {pers1: "John", pers2: "Alice"};

this line is creating a new Object which only contains the keys pers1 and pers2 assigned to the strings "John" and "Alice", you aren't assigning the objects you have created

Upvotes: 0

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