Checking array object existence - arrays

Question

So, I am trying to check the existence of recently pushed array object.
I am developing the web application using angularJS.
I have an array which is defined as
vm.data.detail
So I have a form that let user to CRUD a module. The module is about product stock take. There is a button that will run addProduct() function in my angular controller.
addProduct function:
function addProduct() {
//to check whether the array is empty.
if (vm.data.detail.length == 0) {
vm.data.detail.push({
product: vm.data.product_id.selected,
current_qty: vm.data.product_id.selected.qty,
new_qty: Number(vm.data.product_id.selected.qty) - Number(1),
difference: Number(vm.data.product_id.selected.qty) - (Number(vm.data.product_id.selected.qty) - Number(1)),
remarks: ''
});
console.log("Product just been added");
}
//if the array is not empty
else {
for (var i = 0; i < vm.data.detail.length; i++) {
//to check whether the selected product is already inside the array
if (vm.data.product_id.selected.name == vm.data.detail[i].product.name) {
console.log("same product selected");
//data
}
//if there is no selected product inside the array, then add it
else {
console.log("different product has just been selected");
vm.data.detail.push({
product: vm.data.product_id.selected,
current_qty: vm.data.product_id.selected.qty,
new_qty: 0,
difference: 0,
remarks: ''
});
}
}
}
}
Above code works well when the array just consists of one product. The problem occurs when I am trying to add another product B into the product. Here is the condition :
Product A is already inside the array.
Product B is selected, and then added into the array. Now the array consists of 2 products.
When I am testing to add a new product B, I don't know why the array is still pushed with a new Product B. So now, the array consists of 3 Products (1 Product A, and 2 Product B).
What I wanted is, when I am trying to add the second product B, the array won't be pushed by new product B.
What am I missing here? Have been dealing with it for hours and can't figure out what I have to add for the "validation".
Please note that, the object the array pushing is already correct. I am just don't know how to put the if else. Looks like the logic inside is still lacking of something, but I couldn't figure out what is missing
Thank you so much for the help given.

Answer 1

You're commiting a simple mistake, you are doing the check of else inside the array, you must move it to outside.
Tips:
You can use Array.prototype.find() method to check if the element exists in array, which is much better than perform a traditional for-loop.
As you may have noticed in documentation, the find method have no compatibility with IE and Opera browsers, so if you need this compatibility, you can use Array.prototype.filter().
Below is the code, with both versions (with find and filter) and also with the necessary modifications:
function addProduct() {
//to check whether the array is empty.
if (!vm.data.detail.length) { // you can simply use (!length) instead of comparing with 0
vm.data.detail.push({
product: vm.data.product_id.selected,
current_qty: vm.data.product_id.selected.qty,
new_qty: Number(vm.data.product_id.selected.qty) - Number(1),
difference: Number(vm.data.product_id.selected.qty) - (Number(vm.data.product_id.selected.qty) - Number(1)),
remarks: ''
});
console.log("Product just been added");
}
//if the array is not empty
else {
// if there's no obj with the same name inside the array, it returns undefined, otherwise it returns the object.
var obj = vm.data.detail.find(function(value) {
return value.product.name == vm.data.product_id.selected.name;
});
/* Using FILTER:
var obj = vm.data.detail.filter(function(value) {
return value.product.name == vm.data.product_id.selected.name;
})[0];
*/
// Now you can test, if the object exists
if (obj) {
console.log("same product selected");
}
//if there is no selected product inside the array, then add it
else {
console.log("different product has just been selected");
vm.data.detail.push({
product: vm.data.product_id.selected,
current_qty: vm.data.product_id.selected.qty,
new_qty: 0,
difference: 0,
remarks: ''
});
}
}
}
I hope it helps!

Answer 2

It's a basic logic error. You're doing
for each element {
if element is different from given {
add given to array
}
}
What you need to do is
var allElementsDifferentFromGiven = true
for each element {
if element is same as given {
allElementsDifferentFromGiven = false
break
}
}
if (allElementsDifferentFromGiven) {
add given to array
}
But JavaScript arrays have methods to do that:
if (array.every(function(element) {
return true if element is different given
})) {
add given to array
}

Answer 3

I think problem is here :
because there product is property on Detail object and product does not have name property , it is not matching criteria and going to else condition and pushing into name list.
//to check whether the selected product is already inside the array
if(vm.data.product_id.selected.name == vm.data.detail[i].product.name){
it should be
//to check whether the selected product is already inside the array
if(vm.data.product_id.selected.name == vm.data.detail[i].product){
console.log("same product selected");
//data
}