查找满足测试功能的所有对象索引，例如array.findIndex（）但大于第一个索引

问题描述 投票：0回答：3

我有一个对象数组：

var data = [{"district":"201","date":"Wed Apr 01 2020","paper":671.24,"mgp":36.5},
{"district":"202","date":"Wed Apr 01 2020","paper":421.89,"mgp":44.2},
{"district":"203","date":"Wed Apr 01 2020","paper":607.85,"mgp":67.36},
{"district":"201","date":"Sun Mar 01 2020","paper":571.24,"mgp":38.8},
{"district":"202","date":"Sun Mar 01 2020","paper":421.89,"mgp":36.6},
{"district":"203","date":"Sun Mar 01 2020","paper":607.85,"mgp":69.36},
{"district":"201","date":"Sat Feb 01 2020","paper":571.24,"mgp":38.8},
{"district":"202","date":"Sat Feb 01 2020","paper":421.89,"mgp":22.2},
{"district":"203","date":"Sat Feb 01 2020","paper":607.85,"mgp":59.66},
{"district":"201","date":"Wed Jan 01 2020","paper":571.24,"mgp":38.8},
{"district":"202","date":"Wed Jan 01 2020","paper":421.89,"mgp":22.2},
{"district":"203","date":"Wed Jan 01 2020","paper":607.85,"mgp":89.26}]

[对于每个district，我想获取2月，3月和4月的paper和mgp的值，然后将每个月的值除以其1月的值以测量变化百分比。

使用Array.findIndex（）和reduce（）（例如here），我可以匹配区域并返回正确的值，但是那只会返回匹配的第一个索引，并且由于存在后续月份，所以存在重复索引。我试过绕着findIndex（）绕了几个月的循环无济于事：console.log(result)不返回任何内容

var result = data.reduce((a, b) => {
             var months = [...new Set(a.map(m => a.date))];
             for (var month of months){
              var idx = a.findIndex(e => e.district == b.district && e.date == month)
              if (~idx && b.date === "Wed Jan 01 2020") {
               a[idx].paper = a[idx].paper/b.paper;
               a[idx].mgp = a[idx].mgp/b.mgp} 
              else {
               a.push(JSON.parse(JSON.stringify(b)));
             }
             return a
             }, []);

结果应如下所示：

[{"district":"201","date":"Wed Apr 01 2020","paper":1.17,"mgp":0.94},
 {"district":"202","date":"Wed Apr 01 2020","paper":1,"mgp":1.99},
 {"district":"203","date":"Wed Apr 01 2020","paper":1,"mgp":0.75},
 {"district":"201","date":"Sun Mar 01 2020","paper":1,"mgp":1},
 {"district":"202","date":"Sun Mar 01 2020","paper":1,"mgp":1.64},
 {"district":"203","date":"Sun Mar 01 2020","paper":1,"mgp":0.77},
 {"district":"201","date":"Sat Feb 01 2020","paper":1.17,"mgp":1},
 {"district":"202","date":"Sat Feb 01 2020","paper":1,"mgp":1},
 {"district":"203","date":"Sat Feb 01 2020","paper":1,"mgp":0.67]
javascript multidimensional-array
3个回答
0
投票

var data = [{"district":"201","date":"Wed Apr 01 2020","paper":671.24,"mgp":36.5}, {"district":"202","date":"Wed Apr 01 2020","paper":421.89,"mgp":44.2}, {"district":"203","date":"Wed Apr 01 2020","paper":607.85,"mgp":67.36}, {"district":"201","date":"Sun Mar 01 2020","paper":571.24,"mgp":38.8}, {"district":"202","date":"Sun Mar 01 2020","paper":421.89,"mgp":36.6}, {"district":"203","date":"Sun Mar 01 2020","paper":607.85,"mgp":69.36}, {"district":"201","date":"Sat Feb 01 2020","paper":571.24,"mgp":38.8}, {"district":"202","date":"Sat Feb 01 2020","paper":421.89,"mgp":22.2}, {"district":"203","date":"Sat Feb 01 2020","paper":607.85,"mgp":59.66}, {"district":"201","date":"Wed Jan 01 2020","paper":571.24,"mgp":38.8}, {"district":"202","date":"Wed Jan 01 2020","paper":421.89,"mgp":22.2}, {"district":"203","date":"Wed Jan 01 2020","paper":607.85,"mgp":89.26}]; const byDistrict = {}; for (const item of data) { const month = item.date.split(' ')[1]; // eg Apr if (!byDistrict[item.district]) byDistrict[item.district] = { }; byDistrict[item.district][month] = { paper: item.paper, mgp: item.mgp, date: item.date }; } for (const district of Object.keys(byDistrict)) { const District = byDistrict[district]; District.all = { district, paper: (District.Feb.paper + District.Mar.paper + District.Apr.paper) / District.Jan.paper, mgp: (District.Feb.mgp + District.Mar.mgp + District.Apr.mgp) / District.Jan.mgp } } const result = Object.keys(byDistrict).map(it => byDistrict[it].all); console.log(result);
0
投票
您可以先收集一月值，然后在结果集中省略一月。

var data = [{ district: "201", date: "Wed Apr 01 2020", paper: 671.24, mgp: 36.5 }, { district: "202", date: "Wed Apr 01 2020", paper: 421.89, mgp: 44.2 }, { district: "203", date: "Wed Apr 01 2020", paper: 607.85, mgp: 67.36 }, { district: "201", date: "Sun Mar 01 2020", paper: 571.24, mgp: 38.8 }, { district: "202", date: "Sun Mar 01 2020", paper: 421.89, mgp: 36.6 }, { district: "203", date: "Sun Mar 01 2020", paper: 607.85, mgp: 69.36 }, { district: "201", date: "Sat Feb 01 2020", paper: 571.24, mgp: 38.8 }, { district: "202", date: "Sat Feb 01 2020", paper: 421.89, mgp: 22.2 }, { district: "203", date: "Sat Feb 01 2020", paper: 607.85, mgp: 59.66 }, { district: "201", date: "Wed Jan 01 2020", paper: 571.24, mgp: 38.8 }, { district: "202", date: "Wed Jan 01 2020", paper: 421.89, mgp: 22.2 }, { district: "203", date: "Wed Jan 01 2020", paper: 607.85, mgp: 89.26 }], january = data.reduce((r, o) => { if (o.date.includes('Jan')) r[o.district] = o; return r; }, {}), result = data.reduce((r, o) => { if (o.date.includes('Jan')) return r; r.push({ ...o, paper: +(o.paper / january[o.district].paper).toFixed(2), mgp: +(o.mgp / january[o.district].mgp).toFixed(2) }) return r; }, []); console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }
0
投票

var data = [{"district":"201","date":"Wed Apr 01 2020","paper":671.24,"mgp":36.5}, {"district":"202","date":"Wed Apr 01 2020","paper":421.89,"mgp":44.2}, {"district":"203","date":"Wed Apr 01 2020","paper":607.85,"mgp":67.36}, {"district":"201","date":"Sun Mar 01 2020","paper":571.24,"mgp":38.8}, {"district":"202","date":"Sun Mar 01 2020","paper":421.89,"mgp":36.6}, {"district":"203","date":"Sun Mar 01 2020","paper":607.85,"mgp":69.36}, {"district":"201","date":"Sat Feb 01 2020","paper":571.24,"mgp":38.8}, {"district":"202","date":"Sat Feb 01 2020","paper":421.89,"mgp":22.2}, {"district":"203","date":"Sat Feb 01 2020","paper":607.85,"mgp":59.66}, {"district":"201","date":"Wed Jan 01 2020","paper":571.24,"mgp":38.8}, {"district":"202","date":"Wed Jan 01 2020","paper":421.89,"mgp":22.2}, {"district":"203","date":"Wed Jan 01 2020","paper":607.85,"mgp":89.26}] let res = data.filter(it => !it.date.includes('Jan')) .reduce ((acc, rec) => [...acc, {district: rec.district, date: rec.date, paper: +(rec.paper/data.filter(it => (it.district === rec.district && it.date.includes('Jan')))[0].paper).toFixed(2), mgp: +(rec.mgp/data.filter(it => (it.district === rec.district && it.date.includes('Jan')))[0].mgp).toFixed(2)}] ,[]) console.log(JSON.stringify(res))
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