Avoid using an element's index as the
key prop JS-0437Do not use Array index in keys
10 {data &&
11 products.map((obj, idx) => {
12 return (
13 <div className="mb-10" key={idx}>14 {obj.images ? (
15 <>
16 <div className="card w-72 card-bordered card-compact lg:card-normal border-solid border-black bg-white">Do not use Array index in keys
12 <h1 className="font-bold text-xl">Latest Products</h1>
13 {data.map((p, idx) => {
14 return (
15 <div key={idx}>16 <ProductCard product={p} showDesc={true} />
17 </div>
18 );Do not use Array index in keys
20 {data
21 ? products.map((product, idx) => {
22 return (
23 <div key={idx}>24 <div
25 onClick={() =>
26 router.push(`products/${product.name}`)Do not use Array index in keys
81 ref={idx == posts.length - 1 ? lastPostRef : null}
82 >
83 <Post
84 key={idx} 85 showProductIcon={true}
86 data={p}
87 channel={channel}Do not use Array index in keys
77 posts.map((p, idx) => {
78 return (
79 <div
80 key={idx} 81 ref={idx == posts.length - 1 ? lastPostRef : null}
82 >
83 <Post
Description
When rendering a list of items in React, it is necessary to pass a "key" prop.
This key is used by React to identify which items have changed, are added, or are removed and should be stable.
It is not recommended to use the index of an element as key because it doesn't uniquely identify the element.
When elements are added/removed from an array, the index of an element may change, which will result in unnecessary re-renders.
When the array is sorted, or an element is added to the beginning of the array, the indices will be changed even though the element representing an index may stay the same. This too can result in unnecessary renders.
Bad Practice
cards.map((cardData, index) => (
<Card key={`key-is-${index}`} data={cardData}/>
));
buttonNames.map((btnText, index) => (
<Button key={index} text={btnText}/>
));
things.forEach((thing, index) => {
otherThings.push(<Hello key={index} />);
});
Recommended
cards.map((cardData) => (
<Card key={cardData.id} data={cardData} />
));
buttonData.forEach((btnData) => {
buttons.push(<Hello key={btnData.id} text={btnData.text} />);
});