How to flatten nested array of object using es6
const raw = [
{
id: 1,
country: [
{
id: "5a60626f1d41c80c8d3f8a85"
},
{
id: "5a6062661d41c80c8b2f0413"
}
]
},
{
id: 2,
country: [
{
id: "5a60626f1d41c80c8d3f8a83"
},
{
id: "5a60626f1d41c80c8d3f8a84"
}
]
}
];
const countryIds = raw
.map(x => x.country)
.reduce((acc, curr) => {
return [
...acc,
...curr.map(x => x.id)
];
}, []);
console.log(countryIds)Latest edit
All modern JS environments now support Array.prototype.flat and Array.prototype.flatMap
const data=[{id:1,country:[{id:"5a60626f1d41c80c8d3f8a85"},{id:"5a6062661d41c80c8b2f0413"}]},{id:2,country:[{id:"5a60626f1d41c80c8d3f8a83"},{id:"5a60626f1d41c80c8d3f8a84"}]}];
console.log(
data.flatMap(
(elem) => elem.country
)
)Old answer
No need for any ES6 magic, you can just reduce the array by concatenating inner country arrays.
const data=[{id:1,country:[{id:"5a60626f1d41c80c8d3f8a85"},{id:"5a6062661d41c80c8b2f0413"}]},{id:2,country:[{id:"5a60626f1d41c80c8d3f8a83"},{id:"5a60626f1d41c80c8d3f8a84"}]}];
console.log(
data.reduce(
(arr, elem) => arr.concat(elem.country), []
)
)If you want an ES6 feature (other than an arrow function), use array spread instead of the concat method:
const data=[{id:1,country:[{id:"5a60626f1d41c80c8d3f8a85"},{id:"5a6062661d41c80c8b2f0413"}]},{id:2,country:[{id:"5a60626f1d41c80c8d3f8a83"},{id:"5a60626f1d41c80c8d3f8a84"}]}];
console.log(
data.reduce(
(arr, elem) => [...arr, ...elem.country], []
)
)Note: These suggestions would create a new array on each iteration.
For efficiency, you have to sacrifice some elegance:
const data=[{id:1,country:[{id:"5a60626f1d41c80c8d3f8a85"},{id:"5a6062661d41c80c8b2f0413"}]},{id:2,country:[{id:"5a60626f1d41c80c8d3f8a83"},{id:"5a60626f1d41c80c8d3f8a84"}]}];
console.log(
data.reduce(
(arr, elem) => {
for (const c of elem.country) {
arr.push(c);
}
return arr;
}, []
)
)