SOURCE

var arr = [{
key: '01',
value: '乐乐'
}, {
key: '02',
value: '博博'
}, {
key: '03',
value: '淘淘'
},{
key: '04', 
value: '哈哈'
},{
key: '01',
value: '乐乐'
}]
const obj = {}
const arr1 = arr.reduce((item,next) =>{
    obj[next.key] ? '' : obj[next.key] = true && item.push(next);
    return item
},[])
console.log(arr1)
// const arr2 = arr.map(item => item.value)
console.log( arr.map(item => item.value).includes('乐乐'))