Dummy immutable list implementation in typescript

list.ts

class List<T> {
	_list: T[];
	
	constructor(list: T[]){
		this._list = list;
	}
	
	push(value: T) : List<T> {
		var newValues = this._list.slice(0);
		newValues.push(value);
		
		return new List<T>(newValues);
	}
	
	pop() : List<T> {
		var newValues = this._list.slice(0);
		newValues.pop();
		
		return new List<T>(newValues);		
	}
	
	length() : number {
		return this._list.length;
	}
	
	get(index: number) : T {
		return this._list[index];
	}
}

type someObject = {
	x: number,
	y: number
};

var l = new List<someObject>([]);

var newList = l.push({
	x: 5,
	y: 10
});

console.log(newList.length());