How do you dynamically create new object instances on the fly, using javascript?

Question

I'm trying to create a new instance using a variable from an input field. I've been pushed in the direction of the 'eval()' method, and seeing this is client side code, I don't see this being a problem.
This is my code so far but it is just not working...
```javascript
function createPerson(name, gender, age) {      
    eval( "var " + name + " = new Person()" )
    eval( name + ".details('" + name + "', '" + gender + "', " + age + ")" )
}

createPerson('Liam', 'Male', 2)
```
Well, In the console, this does work, but my other functions in the file can't on it call it. I'm not sure if it would be, seeing the function is called at the same level as the below functions but, would this be scoping issue? 0_o
```javascript
$addAge.on('click', function() {
    Liam.increaseAge()
    Liam.displayHTML()
})

$minusAge.on('click', function() {
    if ( Liam.age <= 0) return;
    Liam.decreaseAge()
    Liam.displayHTML()
})
```
The error I get from this is
```html 
 ReferenceError: Liam is not defined
```
But if I echo out to the console in the function that compiles the new instance, I can access the properties indivdually .
```javascript
    console.log(Liam.name)
    console.log(Liam.gender)
    console.log(Liam.age)
```
returns
```html 
Liam script.js:58:3
Male script.js:59:3
2 script.js:60:3
```

akak · Answer

Hey Liam,
I'm not sure that I understand what you're trying to achieve but here is how I would create an object with those three values and function to add age. Hope that helps somehow :) 
```javascript 
function Person(name, gender, age) {      
        this.name = name;
        this.gender = gender;
        this.age = age;
    }
Person.prototype.addAge = function(age) {
    this.age += age
 }
var liam = new Person('Liam', 'Male', 2);
liam.addAge(2);
console.log(liam);
//outputs:  {name: "Liam", gender: "Male", age: 4}
```

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Liam Maclachlan

Liam Maclachlan

How do you dynamically create new object instances on the fly, using javascript?

Liam Maclachlan

Liam Maclachlan

1 Answer

akak

akak