js 中filter 什么時候加return

結論：寫了{}里面的要return，沒寫{}不加return

大概是寫在{}里面的就算是函數了么？

應該是我ES6箭頭函數沒學好

let arr = [
            {
                id: 1,
                name: 'aa',
                desc: 'aaaa'
            },
            {
                id: 2,
                name: 'bb'
            },
            {
                id: 3,
                name: 'aa'
            }
        ]
        let arr1 = arr.filter(item => item.name == 'aa')//正確
        // let arr2 = arr.filter(item =>  return item.name == 'aa' )  //報錯
        let arr3 = arr.filter(item => {item.name == 'aa'})//為空
        let arr4 = arr.filter(item => { return item.name == 'aa' })//正確
        console.log(arr1, 'arr1') 
        // console.log(arr2, 'arr2');
        console.log(arr3, 'arr3');
        console.log(arr4, 'arr4');

arr1,arr4能正確輸出，arr3沒有取到正確的值是空的，arr2報錯