将对象键/值对拆分为单独的对象

Question

I was wondering is there a way to split key/value pairs of objects and insert them into array so that I get array of objects.

Here is the code:

let grades = [5,5,6,7,6,7,9,10,8,6]

let gradesSpread = {
   5:0,
   6:0,
   7:0,
   8:0,
   9:0,
   10:0
}


// This populates spreadGrades object as intended
for( let [index,grade] in grades.entries() ) {
   gradesSpread[grade]++
}

So now I want to get key/value pair from gradesSpread and create object for each and push it into new array.

I know I can use Object.values() and Object.keys() to get keys or values from object but I have no clue how I would go about adding those key value pairs into array of objects

For better visualization I need array to look something like this :

let finalSpread = [{5:0},{6:4}...]

I am open to all solutions also bonus points for making it so it does not need initialized object.

Answer 1

var arr = [];
Object.keys(grades).forEach((key) => {
    var newObj = {};
    newObj[key] = grades[key];
    arr.push(newObj);
});

Using ES6 it could be shorter:

var arr = [];
Object.keys(grades).forEach((key) => {
    arr.push({[key]: grades[key});
});

Answer 2

You could map the keys with the values. The order does not reflect the order of insertation of the object.

 var object = { 5: 1, 6: 3, 2: 4 }, result = Object .keys(object) .map(k => ({ [k]: object[k] })); console.log(result); 

Answer 3

Sounds like you want Array.prototype.reduce() .

let grades = [5,5,6,7,6,7,9,10,8,6];

let finalSpread = grades.reduce((spread, grade) => {
  let count = spread[grade] || 0;
  spread[grade] = ++count;
  return spread;
}, {});

Seeing as you want a final value that's essentially a map of key-values, I'd recommend finalSpread being an object like above.

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Update:

If it's imperative that it be an array for whatever reason you could:

a. Add finalSpread = Object.entries(finalSpread) at the end (note: each grade will actually be a string)

b. Just refactor the function in reduce to check if they array of [grade, count] already exists and either add it or increment it.

c. use a Map instead of an array as the reduce accumulator (if you need the grades to also be numbers - Map allows non-string keys) - then cast it to an array, ie:

let finalSpread = grades.reduce((spread, grade) => {
  let count = spread.get(grade) || 0;
  spread.set(grade, ++count);
  return spread;
}, new Map());
finalSpread = Array.from(finalSpread);

(note: map and Array.from() have limited browser support.)

Answer 4

You may also try:

let arrayOfObj = [];
let extractPairs = (jsonObj) => {
for(let item in jsonObj) {
    console.log(item);
    arrayOfObj.push({item: jsonObj[item]})
}
console.log(arrayOfObj);
}