Question
Answer and Explanation
Converting JSON to NDJSON (Newline Delimited JSON) involves transforming a single JSON object or an array of JSON objects into a sequence of JSON objects, each on a new line. Handling "array explosions" refers to the process of flattening nested arrays within the JSON structure into individual NDJSON lines. Here's how you can achieve this:
Understanding NDJSON
NDJSON is a format where each line is a valid JSON object. It's commonly used for streaming and processing large datasets because it allows for line-by-line parsing without loading the entire dataset into memory.
Basic JSON to NDJSON Conversion
If your JSON is a single object, the conversion is straightforward:
// Input JSON:
{
"name": "John Doe",
"age": 30
}
// NDJSON Output:
{"name": "John Doe", "age": 30}
If your JSON is an array of objects, each object becomes a line in NDJSON:
// Input JSON:
[
{"name": "John Doe", "age": 30},
{"name": "Jane Smith", "age": 25}
]
// NDJSON Output:
{"name": "John Doe", "age": 30}
{"name": "Jane Smith", "age": 25}
Handling Array Explosions
When your JSON contains nested arrays, you need to "explode" or flatten these arrays into individual NDJSON lines. For example:
// Input JSON:
{
"id": 1,
"items": [
{"name": "Item A", "price": 10},
{"name": "Item B", "price": 20}
]
}
To convert this to NDJSON with array explosion, you would create a new line for each item in the `items` array, possibly including the parent `id`:
// NDJSON Output:
{"id": 1, "name": "Item A", "price": 10}
{"id": 1, "name": "Item B", "price": 20}
Implementation using JavaScript
Here's a JavaScript function to handle this:
function jsonToNdjson(jsonData) {
let ndjson = "";
if (Array.isArray(jsonData)) {
jsonData.forEach(obj => {
ndjson += JSON.stringify(obj) + "\\n";
});
} else if (typeof jsonData === 'object' && jsonData !== null) {
if (jsonData.items && Array.isArray(jsonData.items)) {
jsonData.items.forEach(item => {
const explodedItem = { ...jsonData, ...item };
delete explodedItem.items;
ndjson += JSON.stringify(explodedItem) + "\\n";
});
} else {
ndjson += JSON.stringify(jsonData) + "\\n";
}
}
return ndjson;
}
Explanation:
1. The function `jsonToNdjson` takes JSON data as input.
2. It checks if the input is an array. If so, it iterates through each object and converts it to a line in NDJSON.
3. If the input is an object, it checks for an `items` array. If found, it iterates through the `items`, creates a new object by merging the parent object with each item, removes the original `items` array, and converts it to a line in NDJSON.
4. If no `items` array is found, it converts the object directly to a line in NDJSON.
5. The function returns the complete NDJSON string.
Usage Example:
const jsonData = {
"id": 1,
"items": [
{"name": "Item A", "price": 10},
{"name": "Item B", "price": 20}
]
};
const ndjsonOutput = jsonToNdjson(jsonData);
console.log(ndjsonOutput);
This approach allows you to convert JSON to NDJSON while handling array explosions effectively. You can adapt the JavaScript function to handle more complex nested structures as needed.