useState array as dependency causing infinite loop - reactjs

Question

I have been struggling with this for hours, i'm new to React and would appreciate any assistance.
I'm working on something where users can pick regions into an array.
My main problem is that i want the array that users choose to have unique values only.
I have tried using a javascript SET but that can't be mapped through. The array will be mapped through then displayed to the user.
And i have tried setting "if" statements, that check for duplicate values, inside useEffect but the dependency on a useState array creates an infinite loop.
I have read about using useRef on an array to avoid useEffect infinite loops but i find that its normally for static rather than changing arrays.
Below is the important part:
const [regions, setRegions] = useState([]);
const [region, setRegion] = useState("");
useEffect(() => {
if (region) {
if (regions.includes.region) {
return;
} else if (!regions.includes.region) {
setRegions((prevValue) => {
return [...prevValue, region];
});
}
}
// setRegions((previousState) => new Set([...previousState, region]));
}, [region, regions]);
The rest of the code for context:
import { useEffect, useState } from "react";
import PlacesAutocomplete, {
geocodeByAddress,
getLatLng,
} from "react-places-autocomplete";
export default function Test() {
const [address, setAddress] = useState("");
const [coordinate, setCoordinates] = useState({
lat: null,
lng: null,
});
const [regions, setRegions] = useState([]);
const [region, setRegion] = useState("");
useEffect(() => {
if (region) {
if (regions.includes.region) {
return;
} else if (!regions.includes.region) {
setRegions((prevValue) => {
return [...prevValue, region];
});
}
}
// setRegions((previousState) => new Set([...previousState, region]));
}, [region, regions]);
const handleSelect = async (value) => {
const result = await geocodeByAddress(value);
const full_region = result[0].formatted_address;
const part_region = full_region.substring(0, full_region.indexOf(","));
let province = "";
if (result[0].address_components[2].short_name.length <= 3) {
province = result[0].address_components[2].short_name;
} else {
province = result[0].address_components[3].short_name;
}
setAddress(value);
setCoordinates(coordinate);
setRegion(part_region.concat("-", province));
};
const onDelete = (e) => {
const value = e.target.getAttribute("value");
console.log("onDelete: ", value);
setRegions(regions.filter((item) => item !== value));
};
// setRegions(Array.from(new Set(regions)));
return (
<>
<PlacesAutocomplete
value={address}
onChange={setAddress}
onSelect={handleSelect}
searchOptions={{
componentRestrictions: { country: ["za"] },
types: ["(regions)"],
}}
>
{({ getInputProps, suggestions, getSuggestionItemProps, loading }) => (
<div>
<input
{...getInputProps({
placeholder: "Add regions...",
className: "location-search-input",
})}
/>
<div className="autocomplete-dropdown-container">
{loading && <div>Loading...</div>}
{suggestions.map((suggestion) => {
const className = suggestion.active
? "suggestion-item--active"
: "suggestion-item";
// inline style for demonstration purpose
const style = suggestion.active
? { backgroundColor: "orange", cursor: "pointer" }
: { backgroundColor: "silver", cursor: "pointer" };
return (
<div
key={suggestion.description}
{...getSuggestionItemProps(suggestion, {
className,
style,
})}
>
<span>{suggestion.description}</span>
</div>
);
})}
</div>
</div>
)}
</PlacesAutocomplete>
<p>Regions</p>
<ul>
{regions.map((region) => (
<li
// key={region}
title="remove"
className="cursor-pointer"
onClick={onDelete}
value={region}
>
{region}
</li>
))}
</ul>
</>
);
}

Answer 1

You are using .includes() incorrectly by trying to obtain region as a property: regions.includes.region
This results in:
the second condition else if (!regions.includes.region) always succeeding,
which then results in the state change setRegions() being made,
which then triggers the [regions] in the dependency,
which then loops the useEffect() again, and again.. ..infinitely.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes
Instead, it should be passed as a parameter to the method: if(regions.includes(region)) and if(!regions.includes(region))
useEffect(() => {
if (region) {
if (regions.includes(region)) {
return;
}
if (!regions.includes(region)) {
setRegions((prevValue) => {
return [...prevValue, region];
});
}
}
}, [region, regions]);
You could probably also simplify it by only modifying the state if the condition doesn't succeed:
useEffect(() => {
if (region) {
if (!regions.includes(region)) {
setRegions((prevValue) => {
return [...prevValue, region];
});
}
// else do nothing
}
}, [region, regions]);