jsonparse

const JSONParse = require('jsonparse'); const fs = require('fs'); const path = require('path'); // Imagine this is a very large JSON stream from a file or network. // For demonstration, we use a string and simulate chunks. const largeJsonString = `{ "header": {"requestId": "abc-123", "timestamp": "${new Date().toISOString()}"}, "data": [ {"id": 1, "name": "Item A", "value": 100}, {"id": 2, "name": "Item B", "value": 200}, {"id": 3, "name": "Item C", "value": 300}, {"id": 4, "name": "Item D", "value": 400}, {"id": 5, "name": "Item E", "value": 500} ], "footer": {"processed": true} }`; const parser = new JSONParse(); let processedItemsCount = 0; // The onValue event is fired for every primitive value, and for objects/arrays once they are complete. parser.onValue = function (value, key, parent) { // `this.stack` is an array representing the current path in the JSON structure. // For example, if parsing `{"data": [{"id": 1}]}`, when 'id' is parsed, // this.stack might be ['data', 0, 'id']. // Check if we are inside the 'data' array and the value is a complete item object. // The 'parent' argument is the immediate parent of the current value. // If `key` is null, it means `value` is an element of an array. if (this.stack.length === 1 && this.stack[0] === 'data' && key === null) { // 'value' here is a complete item object (e.g., {"id": 1, "name": "Item A", "value": 100}) console.log('Parsed item:', value); processedItemsCount++; } else if (this.stack.length === 0 && key === 'header') { // Process header object once it's complete console.log('Parsed header:', value); } }; parser.onEnd = function () { console.log(`\nStreaming parse complete. Total items processed: ${processedItemsCount}`); }; parser.onError = function (err) { console.error('Error during JSON parsing:', err.message); process.exit(1); }; // Simulate receiving data in chunks const chunkSize = 50; // Smaller chunks for demonstration for (let i = 0; i < largeJsonString.length; i += chunkSize) { const chunk = largeJsonString.substring(i, i + chunkSize); parser.write(chunk); // In a real application, you might add a small delay here to simulate // network latency, but for this quickstart, immediate writing is fine. } parser.end(); // Signal that no more data will be written. console.log('JSONParse initialized and started processing data stream.');