js new Map()应用

new Map()

// 实现当data数组对象中 time相同时 取code值最大的对象
    let data = [
        {time:'2010-10-11',code:4},
        {time:'2010-10-11',code:2},
        {time:'2010-10-11',code:3},
        {time:'2010-10-12',code:7},
        {time:'2010-10-12',code:3},
        {time:'2010-10-13',code:3},
        {time:'2010-10-14',code:3},
        {time:'2010-10-15',code:3},
        {time:'2010-10-15',code:2},
        {time:'2010-10-15',code:5},
        {time:'2010-10-18',code:5},
        {time:'2010-10-13',code:22},
        {time:'2010-10-17',code:12},
        {time:'2010-10-19',code:12}
    ]

    function unique(arr) {
        const res = new Map()
        arr.forEach(a => {
            !res.has(a.time) && res.set(a.time, a.code)
            res.has(a.time) && a.code >= res.get(a.time) && res.delete(a.time) && res.set(a.time, a.code)
        })
        return [...res].map(v => {return {time:v[0],code:v[1]}})
    }

    console.log(unique(data))
    //处理完成的数据为 : 
    //[ { time: '2010-10-11', code: 4 },
	//  { time: '2010-10-12', code: 7 },
	//  { time: '2010-10-14', code: 3 },
	//  { time: '2010-10-15', code: 5 },
	//  { time: '2010-10-18', code: 5 },
	//  { time: '2010-10-13', code: 22 },
	//  { time: '2010-10-17', code: 12 },
	//  { time: '2010-10-19', code: 12 } ]