I want to counting duplicate item in my array of object,I usse this code below but I have this error : //TypeError: Cannot read properties of undefined (reading 'type')
//this is my array
data[
1:{cs:'10', name:'a' , age},
2:{cs:'20', name :'b', age:'25'},
3:{cs:'10', name :'h', age:'51'},
4:{cs:'10', name :'g', age:'30'},
...]
//this is my result that i want
finalArray[
{cs:'10', count :3},
{cs:'20', count :1 },
...]TypeError: Cannot read properties of undefined (reading 'type')
const prepareSeries = (data, sectors) => {
let finalArray = [{}];
const map = new Map();
finalArray.forEach(function (stockItem) {
if (map.has(stockItem.cs)) {
map.get(stockItem.cs).count++;
} else {
map.set(stockItem.cs, Object.assign(stockItem, { count: 1 }));
}
});
finalArray = [...map.values()];
const result = Object.entries(finalArray)
.sort((a, b) => b[1] - a[1])
.slice(0, 10);
return [
console.log(result),
];
};As I understand it, you want to count the occurrences of unique cs values in your data array? Sure thing.
const data = [
{ cs: "10", name: "a", age: "72" },
{ cs: "20", name: "b", age: "25" },
{ cs: "10", name: "h", age: "51" },
{ cs: "10", name: "g", age: "30" },
];
const countsByCs = {};
data.forEach(({ cs }) => {
countsByCs[cs] = (countsByCs[cs] || 0) + 1;
});
const finalArray = Object.entries(countsByCs)
.map(([cs, count]) => ({ cs, count }))
.sort((a, b) => b.count - a.count);
console.log(finalArray);
outputs
[
{ cs: '10', count: 3 },
{ cs: '20', count: 1 }
]
First, do the counts using Array.prototype.reduce() then sort using Array.prototype.sort().
The following would also work.
const data = [
{ cs: "10", name: "a", age: "31" },
{ cs: "20", name: "b", age: "25" },
{ cs: "10", name: "h", age: "51" },
{ cs: "10", name: "g", age: "30" },
];
const output = Object.entries(
data.reduce((prev, { cs }) => {
prev[cs] = prev[cs] ? prev[cs] + 1 : 1;
return prev;
}, {})
)
.map(([cs, count]) => ({ cs, count }))
.sort((a, b) => b.count - a.count);
console.log(output);Swap a and b in b.count - a.count, if you want to change the order of sorting.