consider the following sample JS Object

const samplejson = [
    {id:'1',value: "AC",},
    {id:'2',value: "AB",},
    {id:'3',value: "AC",},
    {id:'4',value: "AA",},
    {id:'5',value: "AA",},
    {id:'6',value: "AA",},
    {id:'7',value: "AB",},
    {id:'8',value: "AC",},
    {id:'9',value: "AA",},
    {id:'10',value: "AA",},
]

I want to filter the JS object based on the values unique count and descending order like the following

based on the value counts AA - 5, AB - 2 and AC - 3, but I need the output as AA,AC

In react or JS how can achieve this?

CodePudding user response：

You could iterate over any key in the sample data and count each occurrence of a value in a dictionary. Then you can both print the dictionary for a list of amount of occurrences or just the amount of occurrences of one value.

const data = [
    {id:'1',value: "AC",},
    {id:'2',value: "AB",},
    {id:'3',value: "AC",},
    {id:'4',value: "AA",},
    {id:'5',value: "AA",},
    {id:'6',value: "AA",},
    {id:'7',value: "AB",},
    {id:'8',value: "AC",},
    {id:'9',value: "AA",},
    {id:'10',value: "AA",},
]


// make a dict to store and count occurrences
dict = {};

//iterate over every key in your data and keep count in dict
//(initializing it to 1 if it not exists yet)
for(let i = 0; i < data.length; i  ){
  value = data[i].value;
  if(value in dict){
    dict[value]  ;
  }else{
    dict[value] = 1;
  }
}

// here the amount of occurrences are know
console.log(dict);
amountOfAA = dict['AA'];

Output: { AC: 3, AB: 2, AA: 5 } 5

CodePudding user response：

Check this out:

const data = [{id:'1',value: "AC",},{id:'2',value: "AB",},{id:'3',value: "AC",},    {id:'4',value: "AA",},{id:'5',value: "AA",},{id:'6',value: "AA",},{id:'7',value: "AB",},    {id:'8',value: "AC",},{id:'9',value: "AA",},{id:'10',value: "AA",},];

const result = Object.entries(
  data.reduce((acc, { value }) => ({ ...acc, [value]: (acc[value] || 0)   1 }), {})
).sort((a1, a2) => a2[1] - a1[1])
.map(([key]) => key)
.join(',');

console.log(result);

CodePudding user response：

Your desired result can be found using the following steps:

1. Tally the values.
2. Sort the value/count pairs by their count in descending order.
3. Remove the count, leaving only the value.

const items = [
  { id:  '1', value: "AC" },
  { id:  '2', value: "AB" },
  { id:  '3', value: "AC" },
  { id:  '4', value: "AA" },
  { id:  '5', value: "AA" },
  { id:  '6', value: "AA" },
  { id:  '7', value: "AB" },
  { id:  '8', value: "AC" },
  { id:  '9', value: "AA" },
  { id: '10', value: "AA" },
];

const tally = new Map();
for (const { value } of items) {
  if (!tally.has(value)) tally.set(value, 0);
  tally.set(value, tally.get(value)   1);
}

// displaying as object because Map instances show empty in the snippet log
console.log(Object.fromEntries(tally));

const results = Array.from(tally)
  .sort(([,countA], [,countB]) => countB - countA)
  .map(([value]) => value);

console.log(results);