Suppose that we are displaying a large number of data, such as 10thousands of data, there is often a delay in puuting next value to the input field.
In this case, when we enter a value, the screen displays filtered data.
But then, a problem that occurs is the delay in displaying the next action such as input next value to input field due to handling too much data.
・src/Example.js
import { useState } from "react";
const generateDummyItem = (num) => {
return new Array(num).fill(null).map((item, index) => `item ${index}`);
};
const dummyItems = generateDummyItem(10000);
const Example = () => {
const [filterVal, setFilterVal] = useState("");
const changeHandler = (e) => {
setFilterVal(e.target.value);
};
return (
<>
<input type="text" onChange={changeHandler} />
{isPending && <div>Loading...</div>}
<ul>
{dummyItems
.filter((item) => {
if (filterVal === "") return true;
return item.includes(filterVal);
})
.map((item) => (
<li key={item}>{item}</li>
))}
</ul>
</>
);
};
export default Example;
- To solve the problem, we can wrap the
setFilterValfunction with a startTransition.
const changeHandler = (e) => {
startTransition(() => {
setFilterVal(e.target.value);
})
};
The startTransition makes a function delay to be executed within it.
Thanks to this feature, we can easily move on to the next value in the input field.
・Before input
・After input
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