在 map 函数中分配一个 const 变量

Question

I'm using Reactivesearch, and I'm trying to assign a const variable inside a map function. Specifically in the .map Like such:

onAllData(data, streamData) {

    return (
        <div className="grid">
        {
            data.map((item) => 
                const propertyName = item.productName;

                <div className="flex-container card" key={item._id}>
                    <div className="content">
                        <p>{propertyName}</p>
                    </div>
                </div>
            )
        }
    );
}

const propertyName = item.productName; is giving me problem. Error states unexpected token .

Is it possible?

Answer 1

You need to go from expression syntax to the block syntax, using braces and return :

        data.map((item) => {
            const propertyName = item.productName;

            return (<div className="flex-container card" key={item._id}>
                <div className="content">
                    <p>{propertyName}</p>
                </div>
            </div>)
        })

However, you could also use destructuring to get your propertyName , and then you are back to one expression:

        data.map(({productName, _id}) =>
           <div className="flex-container card" key={_id}>
                <div className="content">
                    <p>{propertyName}</p>
                </div>
            </div>
        )

Answer 2

That is an improper use of arrow functions.

Fix:

data.map(({productName, _id}) => (
   <div className="flex-container card" key={_id}>
       <div className="content">
            <p>{productName}</p>
        </div>
   </div>
);