Source contract and expected records
This is an original, fully synthetic mapping example. Inputs are plain, acyclic JSON-shaped records with the fields shown; the canonical shape and rejection codes belong to this example. Adapt the contract before using a different source.
For this acyclic JSON-shaped payload, recursively visit object fields. Emit scalar leaves with a path array. Arrays of scalars remain one whole answer; object-valued arrays are rejected. Emit an empty object as an explicit {} answer rather than omitting it. Path arrays preserve field-name boundaries without joining them into text.
| Case | Input record (JSON) | Expected output (JSON) |
|---|---|---|
| Capture nested answer leaves | {"payload":{"profile":{"name":"Ada","tags":["new","trial"]},"optIn":false}} | {"ok":true,"value":{"answers":[{"path":["profile","name"],"value":"Ada"},{"path":["profile","tags"],"value":["new","trial"]},{"path":["optIn"],"value":false}]}} |
| Reject object-valued array | {"payload":{"tags":[{"code":"new"}]}} | {"ok":false,"error":"LEAF_ARRAY"} |
| Preserve empty object | {"payload":{"profile":{}}} | {"ok":true,"value":{"answers":[{"path":["profile"],"value":{}}]}} |
Run the local transformation
Run the complete example as a JavaScript module in Node.js. It contains the pure mapping function, all three inputs and literal expected outputs; assertions stop on a mismatch. A rejected case returns ok=false with an error code, rather than a partial canonical record.
import assert from 'node:assert/strict';
function leafAnswers(i){
const fail=error=>({ok:false,error});if(!i||!Object.hasOwn(i,'payload'))return fail('LEAF_PAYLOAD');
const scalar=v=>v===null||typeof v==='string'||typeof v==='boolean'||(typeof v==='number'&&Number.isFinite(v));
const answers=[];let error;
const visit=(value,path)=>{
if(scalar(value)){answers.push({path,value});return;}
if(Array.isArray(value)){if(!value.every(scalar)){error='LEAF_ARRAY';return;}answers.push({path,value:[...value]});return;}
if(value&&typeof value==='object'){
const entries=Object.entries(value);if(!entries.length){answers.push({path,value:{}});return;}
for(const [key,v]of entries)visit(v,[...path,key]);return;
}
error='LEAF_VALUE';
};
visit(i.payload,[]);return error?fail(error):{ok:true,value:{answers}};
}
// Original synthetic cases; expected outputs are literal records.
const cases = [
{
"label": "Capture nested answer leaves",
"input": {
"payload": {
"profile": {
"name": "Ada",
"tags": [
"new",
"trial"
]
},
"optIn": false
}
},
"expected": {
"ok": true,
"value": {
"answers": [
{
"path": [
"profile",
"name"
],
"value": "Ada"
},
{
"path": [
"profile",
"tags"
],
"value": [
"new",
"trial"
]
},
{
"path": [
"optIn"
],
"value": false
}
]
}
}
},
{
"label": "Reject object-valued array",
"input": {
"payload": {
"tags": [
{
"code": "new"
}
]
}
},
"expected": {
"ok": false,
"error": "LEAF_ARRAY"
}
},
{
"label": "Preserve empty object",
"input": {
"payload": {
"profile": {}
}
},
"expected": {
"ok": true,
"value": {
"answers": [
{
"path": [
"profile"
],
"value": {}
}
]
}
}
}
];
for (const sample of cases) {
const actual = leafAnswers(sample.input);
assert.deepEqual(actual, sample.expected);
console.log(sample.label, JSON.stringify(actual));
}
Work through the boundary
Does tags=["new","trial"] produce two separate indexed answers?
Show the worked answer
No. It remains one answer at ["profile","tags"] with the full array. optIn=false is another explicit answer, while an empty profile produces an answer value {}.