Approach: Walk the input object recursively and build a shallow-deep copy while applying redaction when a path matches. Do not mutate the input — create new objects/arrays on the fly. Support dot-separated paths like "user.email" and handle arrays by descending into each element automatically (no special syntax required).javascript
// Node.js / JavaScript implementation
const REDACTED = '[REDACTED]';
/**
* Redact PII from obj according to redactionPaths (e.g. ['user.email','payment.card.number'])
* Returns a new object, does not mutate input.
*/
function redactPII(obj, redactionPaths) {
const pathTrees = buildPathTree(redactionPaths);
return redactNode(obj, pathTrees);
}
function buildPathTree(paths) {
// Build a trie-like tree for fast matching
const root = {};
for (const p of paths) {
const parts = p.split('.');
let node = root;
for (const part of parts) {
node[part] = node[part] || {};
node = node[part];
}
node.__redact = true;
}
return root;
}
function redactNode(node, pathTree) {
// primitive or null -> return as-is
if (node === null || typeof node !== 'object') return node;
if (Array.isArray(node)) {
// map each element, applying same pathTree
return node.map(el => redactNode(el, pathTree));
}
// object: copy keys; for each key check pathTree
const out = {};
for (const [k, v] of Object.entries(node)) {
if (pathTree && pathTree[k]) {
if (pathTree[k].__redact) {
// redact the whole value at this path
out[k] = REDACTED;
} else {
// descend with the subtree for this key
out[k] = redactNode(v, pathTree[k]);
}
} else {
// key not in any redaction path: still need to deep-copy to avoid mutation
out[k] = redactNode(v, null);
}
}
return out;
}
