Is there a way to extract all the values associated with the property code within nested arrays of objects, regardless of how deeply they are nested?
[
{code: '1', children: [
{code: '11'}, {code: '12'}
]},
{code: '2', children: [
{code: '21'}, {code: '22', children: [{code: '221'}]}
]},
]
The desired output should be : [1, 11, 12, 2, 21, 22, 221]
flatMap is a valuable tool in situations like this, and can be paired with a recursive function, destructuring function parameters using default values, and array rest syntax.
const flatten = arr => arr.flatMap(
({ code, children=[] }) => [code, ...flatten(children)])
const flatten = arr => arr.flatMap(
({ code, children=[] }) => [code, ...flatten(children)])
const arr = [
{ code: '1', children: [{ code: '11' }, { code: '12' }] },
{ code: '2', children: [{ code: '21' }, { code: '22', children: [{ code: '221' }] }],},
]
console.log(flatten(arr))In case you didn't know, the structure you're working with is known as a tree, it would be beneficial to delve deeper into its concepts, especially exploring the various traversal methods such as dfs and bfs.
Exploring generator functions with examples of depth-first search (DFS) and breadth-first search (BFS)
const laziness = [{
code: 'A',
children: [{
code: 'A1'
}, {
code: 'A2'
}]
},
{
code: 'B',
children: [{
code: 'B1'
}, {
code: 'B2',
children: [{
code: 'B21'
}]
}]
},
]
console.log([...bfs(laziness)])
console.log([...dfs(laziness)])
// breadth-first search
function* bfs(items) {
const queue = [...items]
while (queue.length) {
const item = queue.shift()
yield + item.code
if (item.children) {
queue.push(...item.children)
}
}
}
// depth-first search
function* dfs(items) {
for (const item of items) {
yield + item.code
if (item.children) {
yield* dfs(item.children)
}
}
}To efficiently accomplish this task, you can utilize recursion along with the flatMap method in JavaScript:
function extractCodes(data) {
return data.flatMap((item) => {
const children = item.children ? extractCodes(item.children) : [];
return [+item.code, ...children];
});
}
const sampleData = [
{ code: '001', children: [{ code: '0011' }, { code: '0012' }] },
{ code: '002', children: [{ code: '0021' }, { code: '0022', children: [{ code: '00221' }] }],},
];
function extractCodes(data) {
return data.flatMap((item) => {
const children = item.children ? extractCodes(item.children) : [];
return [+item.code, ...children];
});
}
console.log(extractCodes(sampleData));To achieve the desired outcome, recursion can be implemented:
function extractCode (nestedArray, current = []){
nestedArray.forEach((element)=>{
if ('code' in element) current.push(element.code)
const keys = Object.keys(element);
keys.forEach(key => {
if (Array.isArray(element[key]) extractCode(element[key], current);
}
return current;
}
extractCode([
{code: '1', children: [{code: '11'}, {code: '12'}]},
{code: '2', children: [{code: '21'}, {code: '22', children: [{code: '221'}]}]},
])
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