App-Object.js

var app = {
    db: {},
    next_id: 0,
    create: function(newThing) {
        // this.db[this.next_id] = newThing;
        // this.next_id ++;
        if(newThing !== ''){
        	this.db[this.next_id] = newThing;
        	this.next_id ++;
        	console.log("THING WAS ADDED")
        	return 'THING WAS ADDED';
        }else{
        	console.log("ERROR")
        	return 'new value was an empty string, nopes.';
        }
    },
    read: function(ID) {
        if(this.db[ID]){
        	return this.db[ID]; 
        } else {
        	return 'NOT FOUND';  
        }
    },
    update: function(ID, new_value) {
        var returner = '';
        if (this.db[ID] && new_value !== ""){
            returner ='All good';
        } else if (this.db[ID] && new_value === ""){
            returner ='Bad input';
        } else if (this.db[ID] !==undefined && new_value !== ""){
            returner ='Bad id';
        } else{
            returner ='Bad id & bad input';
        }  
	    return returner
    },
    delete: function(ID) {
		if(this.db[ID]){
			this.db[ID] = undefined;
			console.log('item WAS DELETED');
		} else{
			console.log('UNKNOWN ID');
		}
    }
};

console.log(app.update(0, "Marta"));

function app_handler() {
	// read user input from dom

	var result = app.create(user_input);

	// write result to dom
}

Trying to make work the update part