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Validate Duplicate Data Entry in Array - JavaScript

My problem is that I want to insert values that are not repeated when doing a push
This is my code :
addAddress: function() {
this.insertAddresses.Adress = this.address_address
this.insertAddresses.State = this.selectedStateAddress
this.insertAddresses.City = this.selectedCityAddress
if(this.insertAddresses.Adress !== "" && this.insertAddresses.State !== null && this.insertAddresses.City !== null) {
let copia = Object.assign({}, this.insertAddresses);
this.addresses.push(copia)
}
else
{
this.$message.error('Not enough data to add');
return
}
},
When adding a new element to my object, it returns the following.
When I press the add button again, it adds the same values again, I want to perform a validation so that the data is not the same. How could I perform this validation in the correct way?

Verify that the item doesn't already exist in the array before inserting.
You can search the array using Array.prototype.find:
export default {
methods: {
addAddress() {
const newItem = {
Address: this.address_address,
State: this.selectedStateAddress,
City: this.selectedCityAddress
}
this.insertItem(newItem)
},
insertItem(item) {
const existingItem = this.addresses.find(a => {
return
a.State === item.State
&& a.City === item.City
&& a.Address === item.Address
})
if (!existingItem) {
this.addresses.push(item)
}
}
}
}
On the other hand, if your app requires better performance (e.g., there are many addresses), you could save a separate dictonary to track whether the address already exists:
export default {
data() {
return {
seenAddresses: {}
}
},
methods: {
insertItem(item) {
const { Address, State, City } = item
const key = JSON.stringify({ Address, State, City })
const seen = this.seenAddresses[key]
if (!seen) {
this.seenAddresses[key] = item
this.addresses.push(item)
}
}
}
}
demo

check it:
let filter= this.addresses.find(x=> this.insertAddresses.State==x.State)
if (filter==null) {
this.$message.error('your message');
}
OR FILTER ALL
let filter= this.addresses.find(x=> this.insertAddresses.Adress==x.Adress && this.insertAddresses.State==x.State && this.insertAddresses.City==x.City)
if (filter==null) {
this.$message.error('your message');
}
``

How do I avoid infinite loop when using Redux state in useEffect dependency array?

I'm trying to figure out why my useEffect function ends up in an infinite loop.
I have two variables that are hooked into my Redux store:
const vehicles: AllVehiclesCollection = useSelector((state: ReduxState) => state.claims?.vehicles ?? {});
const properties: AllPropertiesCollection = useSelector((state: ReduxState) => state.claims?.properties ?? {});
and I have an action that is dispatched to the store that updates these only after a user clicks a button.
I have a useEffect that will trigger based on either of these variables changing.
useEffect(() => {
let fullVehicleList: DropdownData[] = getFormattedVehicleListForDisplay();
let fullPropertyList: DropdownData[] = getFormattedPropertyListForDisplay();
let fullList = fullVehicleList.concat(fullPropertyList);
if (fullList.length > 0) {
setVehiclesAndPropertiesList(fullList);
} else {
setVehiclesAndPropertiesList(null);
}
}, [vehicles, properties]);
Nowhere in this code are the vehicles or properties variables changed or any actions dispatched that would change the Redux state.
getFormattedVehicleListForDisplay function:
const getFormattedVehicleListForDisplay = () => {
let list: DropdownData[] = [];
if (Object.keys(vehicles).length > 0) {
let thisPolicysVehicles = [];
if (vehicles !== null) {
const key = `${selectedPolicy.symbol}${selectedPolicy.number}`;
thisPolicysVehicles = vehicles[key];
}
if (thisPolicysVehicles && thisPolicysVehicles.length > 0) {
thisPolicysVehicles.forEach((vehicle: VehicleInformation) => {
if (vehicle.vehicleMake !== OTHER_VEHICLE) {
list.push({
label: formatVehicleForDisplay(vehicle),
value: { ...vehicle, type: 'V' },
});
} else {
list.push({ label: vehicle.vehicleMake, value: {} });
}
});
}
}
return list;
};
getFormattedPropertyListForDisplay function:
const getFormattedPropertyListForDisplay = () => {
let list: DropdownDataOMIG[] = [];
if (Object.keys(properties).length > 0) {
let thisPolicysProperties = [];
if (properties !== null) {
const key = `${selectedPolicy.symbol}${selectedPolicy.number}`;
thisPolicysProperties = properties[key];
}
if (thisPolicysProperties && thisPolicysProperties.length > 0) {
thisPolicysProperties.forEach((property: LocationInformation) => {
if (property.locStreet1 !== OTHER_PROP) {
list.push({
label: formatPropertyForDisplay(property),
value: { ...property, type: 'P' },
});
} else {
list.push({ label: property.locStreet1, value: {} });
}
});
}
}
return list;
};
For reference, the data in vehicles and properties is a set of key-value pairs where the key is a unique identifier of a given account number and the value is an array of vehicle/property objects for that account.
Any idea why this goes into an infinite loop when using Redux state in the dependency array? Is there a different way to use Redux state in a dependency array? Thanks!

When using
const vehicles = useSelector((state: ReduxState) => state.claims?.vehicles ?? {});
Each time this is triggered, and you don't have vehicles in your store, you return a new object {}. and {} === {} // false
So ain your useEffect dependency array, it's each time a new Object, so useEffect is triggered.
So either remove your || {} in your selector (because null === null & undefined === undefined) or consider moving to useShallowSelector as explained in react-redux documentation

prevent duplicate objects being added to state react redux

I have a question regarding preventing duplicates from being added to my redux store.
It should be straight forward but for some reason nothing I try is working.
export const eventReducer = (state = [], action) => {
switch(action.type) {
case "ADD_EVENT":
return [...state, action.event].filter(ev => {
if(ev.event_id !== action.event.event_id){
return ev;
}
});
default:
return state;
}
};
The action looks something like the below:
{
type: "ADD_EVENT",
event: { event_id: 1, name: "Chelsea v Arsenal" }
}
The issue is that on occasions the API I am working with is sending over identical messages through a websocket, which means that two identical events are getting added to my store.
I have taken many approaches but cannot figure out how to get this to work. I have tried many SO answers,

Why your code is failing?
Code:
return [...state, action.event].filter(ev => {
if(ev.event_id !== action.event.event_id){
return ev;
}
});
Because first you are adding the new element then filtering the same element, by this way it will never add the new value in the reducer state.
Solution:
Use #array.findIndex to check whether item already exist in array or not if not then only add the element otherwise return the same state.
Write it like this:
case "ADD_EVENT":
let index = state.findIndex(el => el.event_id == action.event.event_id);
if(index == -1)
return [...state, action.event];
return state;

You can use Array.prototype.find().
Example (Not tested)
const eventExists = (events, event) => {
return evets.find((e) => e.event_id === event.event_id);
}
export const eventReducer = (state = [], action) = > {
switch (action.type) {
case "ADD_EVENT":
if (eventExists(state, action.event)) {
return state;
} else {
return [...state, action.event];
}
default:
return state;
}
};
Update (#CodingIntrigue's comment)
You can also use Array.prototype.some() for a better approach
const eventExists = (events, event) => {
return evets.some((e) => e.event_id === event.event_id);
}
export const eventReducer = (state = [], action) = > {
switch (action.type) {
case "ADD_EVENT":
if (eventExists(state, action.event)) {
return state;
} else {
return [...state, action.event];
}
default:
return state;
}
};

Solution:
const eventReducer = ( state = [], action ) => {
switch (action.type) {
case 'ADD_EVENT':
return state.some(( { event_id } ) => event_id === action.event.event_id)
? state
: [...state, action.event];
default:
return state;
}
};
Test:
const state1 = eventReducer([], {
type: 'ADD_EVENT',
event: { event_id: 1, name: 'Chelsea v Arsenal' }
});
const state2 = eventReducer(state1, {
type: 'ADD_EVENT',
event: { event_id: 2, name: 'Chelsea v Manchester' }
});
const state3 = eventReducer(state2, {
type: 'ADD_EVENT',
event: { event_id: 1, name: 'Chelsea v Arsenal' }
});
console.log(state1, state2, state3);

You can something like this, for the logic part to ensure you don't get the same entry twice.
const x = filter.arrayOfData(item => item.event_id !== EVENT_FROM_SOCKET);
if (x.length === 0) {
// dispatch action here
} else {
// ignore and do nothing
}

You need to be careful when using Arrays in reducers. You are essentially adding more items to the list when you call:
[...state, action.event]
If you instead use a map then you can prevent duplicates
const events = { ...state.events }
events[action.event.event_id] = action.event.name]
{...state, events }

If duplicate exist in previous state then we should return same state else update the state
case "ADDPREVIEW":
let index = state.preview.findIndex(dup => dup.id == action.payload.id);
return {
...state,
preview: index == -1 ? [...state.preview,action.payload]:[...state.preview]
};

React calling action results infinite loop

I have the following component. I want to run an action (this.props.selectCharacter) if condition is met. However, this results in an infinite loop currently maximum call stack exceeded
components/board.js
componentDidUpdate() {
this.props.characters.map((character) => {
// if the character is located correctly
if(character.found === true) {
// hide the overlay
document.getElementById(character.id).style.display = 'none';
// go to next character
var nextCharacter = {
id: '_x30_2-A-Kenard',
name: 'Kenard',
'avatar': 'img/2.jpg',
found: false
};
this.props.selectCharacter(nextCharacter);
}
});
}
actions/index.js
export function selectCharacter(character) {
// Action creator; needs to return an action (an object with a type property)
return {
type: 'CHARACTER_ACTIVATED',
payload: character
};
}
reducers/reducer_active_character.js
export default function(state = { id: '_x30_1-A-RussellStringerBell', name: 'Stringer Bell', avatar: 'img/1.jpg', found: false }, action) {
switch(action.type) {
case 'CHARACTER_ACTIVATED':
return action.payload;
}
return state;
}

Your issue is if one of character.found === true will update characters, which leads component update. '
console.log(characters) in your reducer, found is there a character.found === true
Change your componentDidUpdate like:
const newCharacters = character.map(c => {
return c.found ? { // new character } : c;
});
this.props.selectCharacters(newCharacters);

How to write state changing routine, similar to Redux?

How can I write a really super, simple state changing routine? I need something like Redux, but way simpler, don't need all the bells & whistles.
I was thinking of a global object i.e. myState = {}, that is changed via setMyState() / getMyState().
I'm using JavaScript, and wondering if this would be done via a timer that polls say every 10ms, or so.
So in my JavaScript client app (I'm using ReactJS), a call to my getMyState("show-menu") inside a render() would update the Component's state just like using this.state..
The reason I want this is:
1) Wanna know how to write it for learning purposes.
2) Need something simpler that Redux, simple like Meteor's Session vars, so don't have to pass this.Refs. down to child compnents which setState on parent components.
3) Redux is a mouthful, there is still lots to digest and learn to use Redux.

Seems like you could do this pretty simply with a constructor.
function State () {
this._state = {};
...
}
State.prototype.get = function () {
return this._state;
};
State.prototype.set = function (state) {
return this._state = state;
};
var STATE = new State();
But then you have to do the polling you mentioned in your post. Alternatively, you can look at eventEmitter libraries for javascript, for example https://github.com/facebook/emitter, and turn the State object into an event emitter.

Update
Not sure if this is what you're looking for, at all, but it's simpler.
function makeStore () {
var state = { };
return {
set (key, value) { state[key] = value; },
get (key) { return state[key]; }
};
}
const store = makeStore();
store.set("counter", 1);
store.get("counter"); // 1
Believe it or not, there's really not a lot to Redux.
There's, perhaps, a lot to think about, and it's extra work to keep everything untied from your store...
But have a quick look:
function reducer (state, action) {
state = state || { count: 0 };
const direction = (action.type === "INCREASE") ? 1 : (action.type === "DECREASE") ? -1 : 0;
return {
count: (state.count + direction)
};
}
function announceState () {
console.log(store.getState());
}
function updateView () {
const count = store.getState().count;
document.querySelector("#Output").value = count || 0;
}
function increase () {
store.dispatch({ type: "INCREASE" });
}
function decrease () {
store.dispatch({ type: "DECREASE" });
}
const store = createStore(reducer, { count: 0 });
store.subscribe(announceState)
.subscribe(updateView);
document.querySelector("#Increment").onclick = increase;
document.querySelector("#Decrement").onclick = decrease;
updateView();
This is the code I intend to use.
Looking at it, I'm pretty much just creating a store (with a function to run every time there's an event), there's the subscription to have a listener run, after the store has updated, there's a line where I fire an action, and... ...well, that's it.
function createStore (reduce, initialState) {
var state = initialState;
var listeners = [];
function notifyAll () {
listeners.forEach(update => update());
}
function dispatch (event) {
const newState = reduce(state, event);
state = newState;
notifyAll();
return store;
}
function subscribe (listener) {
listeners.push(listener);
return store;
}
function getState () {
return state;
}
const store = {
getState, subscribe, dispatch
};
return store;
}
// THIS IS MY APPLICATION CODE
function reducer (state, action) {
state = state || { count: 0 };
const direction = (action.type === "INCREASE") ? 1 : (action.type === "DECREASE") ? -1 : 0;
return {
count: (state.count + direction)
};
}
function announceState () {
console.log(store.getState());
}
function updateView () {
const count = store.getState().count;
document.querySelector("#Output").value = count || 0;
}
function increase () {
store.dispatch({ type: "INCREASE" });
}
function decrease () {
store.dispatch({ type: "DECREASE" });
}
const store = createStore(reducer, { count: 0 });
store.subscribe(announceState)
.subscribe(updateView);
document.querySelector("#Increment").onclick = increase;
document.querySelector("#Decrement").onclick = decrease;
updateView();
<button id="Decrement">-</button>
<output id="Output"></output>
<button id="Increment">+</button>
The very tiny, very easy implementation of a store (note that the real thing is more complex) is above. dispatch and subscribe are very useful, here.