Destruct using titles | 易学教程

问题

I have answered a few questions using destructing, I just want to take this one to the next level

I want to not use reduce in this example but pure destructing if at all possible

So the data's first row contains the attribute names of the object, How can I use that to be DRY

i.e. I hoped for

const obj = data.slice(1).map((titles) => ({ titles }) )

or similar

So this works, but I miss one more step:

const data = [
    ["fruits","frozen","fresh","rotten"],
    ["apples",884,494,494],
    ["oranges",4848,494,4949],
    ["kiwi",848,33,33]
]
const titles = data[0]; // not used below but I want to use it
const obj = data.slice(1).map(([fruits,frozen,fresh,rotten]) => ({ fruits,frozen,fresh,rotten }) )
console.log(obj)

回答1:

You could map the entries for an object.

const
    data = [["fruits", "frozen", "fresh", "rotten"], ["apples", 884, 494, 494], ["oranges", 4848, 494, 4949], ["kiwi", 848, 33, 33]],
    mapWith = keys => values => Object.fromEntries(keys.map((k, i) => [k, values[i]])),
    getArray = ([keys, ...data]) => data.map(mapWith(keys)),
    array = getArray(data);

console.log(array);

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Old simpler example

const data = [
  ["fruits", "frozen", "fresh", "rotten"],
  ["apples", 884, 494, 494],
  ["oranges", 4848, 494, 4949],
  ["kiwi", 848, 33, 33]
]
const titles = data[0];

const obj = data.slice(1).map(
  arr => Object.fromEntries(
    titles.map( 
      (t, i) => [t, arr[i]] 
    )
  )
);

console.log(obj);

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回答2:

You can create a curried version of zip which is similar to Object.fromEntries except that it doesn't take pairs but a list of keys and a list of values and pairs are formed based on indexes:

zip(['a','b'], [1,2]);
//=> {a: 1, b: 2})

Because it is curried you can use it in your map and avoid hardcoding titles:

const data = [
    ["fruits","frozen","fresh","rotten"],
    ["apples",884,494,494],
    ["oranges",4848,494,4949],
    ["kiwi",848,33,33]
]

const zip =
  keys =>
    values =>
      Object.fromEntries
        ( keys.map((k, i) => [k, values[i]])
        );
        
const from_csv =
  ([titles, ...rows]) =>
    rows.map(zip(titles));

console.log(
  from_csv(data)
);

回答3:

You could use reduce, but you can't really destruct...

const data = [
    ["fruits","frozen","fresh","rotten"],
    ["apples",884,494,494],
    ["oranges",4848,494,4949],
    ["kiwi",848,33,33]
]
const titles = data[0];
const obj = data.slice(1).map((row) => titles.reduce((agg, cur, index) => {
   agg[cur] = row[index];
   return agg;
}, {}));
console.log(obj)

回答4:

const data = [
    ["fruits","frozen","fresh","rotten"],
    ["apples",884,494,494],
    ["oranges",4848,494,4949],
    ["kiwi",848,33,33]
];
const [titles, ...rest] = data;
const obj = rest.map((xs) => {
  const o = {};
  xs.forEach((x,i) => o[titles[i]] = x);
  return o;
});
console.log(obj);

来源：https://stackoverflow.com/questions/62197270/destruct-using-titles

标签

javascript

arrays

destructuring