Question

I’m trying to create a new class, but it doesn’t seem to be working. Here’s the code:

<script>
var myClass = function(arg){
    return new init(arg);
}
var init = function(arg){
    return arg;
}
init.prototype.prop = true;
</script>

The problem is that myClass('foo') doesn’t return 'foo' as expected. Instead, it returns init.
Then I tried this code:

var init = function(arg){
    return [arg];//Now init returns an array
}

The myClass('foo') returns ['foo'], but then myClass('foo').prop turns into undefined. Does anyone know how to solve it?

EDIT: I want to create this class more or less as jQuery does.
For example: $('div') returns directly a value (in case, all div tags), but not an object with a property that stores this values

Answer 1

When you call new init() and within init() you return a non-object, it yields an instance of init instead of the returned value.

If you return an Array from your init() function, it gets returned instead; but Array doesn’t take your init prototype into consideration 🙂

See also: https://stackoverflow.com/a/1978474/1338292

If you want to be like an array, you can do this:

function myClass(arg) {
    return new init(arg);
}
function init(arg) {
    this.push(arg);
}
init.prototype = [];
init.prototype.foo = true;

var x = new init('foo');
console.log(x) // ["foo"]
console.log(x.foo) // true

It makes init inherit from the Array prototype (i.e. []). After that you can add more properties and methods to the init prototype as you wish.