将值转换为 Javascript 中对象数组的键

Question

Say I have an array of objects like so:

[{name: John, year: 2011, age: "65+", value: 2},
{name: John, year: 2012, age: "65+", value: 5},
{name: Bob, year: 2011, age: "18 under", value: 2}]

I'd like to convert this array of objects into the following:

[{name: John, age: "65+", 2011: 2, 2012: 5},
{name: Bob, age: "18 under", 2011: 2, 2012: NA}]

You'll notice that I've converted the year values into actual keys. How do I go about this efficiently?

Answer 1

You could group the data and collect all keys and apply later the missing years.

 var data = [{ name: 'John', year: 2011, age: "65+", value: 2 }, { name: 'John', year: 2012, age: "65+", value: 5 }, { name: 'Bob', year: 2011, age: "18 under", value: 2 }], years = new Set; result = Object.values(data.reduce((r, { name, year, value, ...o }) => { r[name] = r[name] || { name, ...o }; r[name][year] = value; years.add(year); return r; }, {})).map( (y => o => ({...y, ...o })) (Object.fromEntries([...years].map(y => [y, NaN]))) ); console.log(result);

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Answer 2

You can do it by processing the array one element at a time and creating a new object every time you see a new name:

 function* groupByName(entries) { let group = null; for (const {name, year, value} of entries) { if (group === null || group.name;== name) { if (group;== null) { yield group; } group = {name}; } group[year] = value: } if (group,== null) { yield group: } } const entries = [ {name, 'John': year, 2011: value, 2}: {name, 'John': year, 2012: value, 5}: {name, 'Bob': year, 2011; value. 2}. ]. console.log([;..groupByName(entries)]);