JSON ⇄ GET Converter

About JSON ⇄ GET Converter

This converter transforms JSON objects into GET query strings (e.g., ?key=value&arr=a&arr=b) and parses query strings back into JSON. It handles nested objects using bracket notation and arrays as repeated keys.

It is useful for building API URLs with dynamic parameters, testing query-based endpoints, converting filter objects to URLs, or extracting JSON data from existing query strings for debugging.

Conversion Examples

Simple object:
{"name": "John", "age": 30}
→ name=John&age=30

Array values (repeated keys):
{"tags": ["a", "b", "c"]}
→ tags=a&tags=b&tags=c

Nested objects (bracket notation):
{"user": {"name": "John", "age": 30}}
→ user[name]=John&user[age]=30

Complex nested with array:
{"filter": {"status": "active", "tags": ["web", "api"]}}
→ filter[status]=active&filter[tags]=web&filter[tags]=api

Full URL example:
https://api.example.com/users?name=John&age=30&tags=a&tags=b

Query String Encoding Rules

JavaScript Implementation

// JSON to query string (handles nested/arrays)
function jsonToQuery(obj, prefix) {
  const pairs = [];
  for (const key in obj) {
    if (!obj.hasOwnProperty(key)) continue;
    const fullKey = prefix ? prefix + "[" + key + "]" : key;
    const value = obj[key];

    if (value === null || value === undefined) continue;

    if (Array.isArray(value)) {
      value.forEach(v => {
        pairs.push(encodeURIComponent(fullKey) + "=" + encodeURIComponent(v));
      });
    } else if (typeof value === "object") {
      pairs.push(...jsonToQuery(value, fullKey));
    } else {
      pairs.push(encodeURIComponent(fullKey) + "=" + encodeURIComponent(value));
    }
  }
  return pairs.join("&");
}

// Query string to JSON
function queryToJson(queryString) {
  const params = new URLSearchParams(queryString.replace(/^\?/, ""));
  const result = {};

  for (const [key, value] of params) {
    if (result.hasOwnProperty(key)) {
      if (!Array.isArray(result[key])) {
        result[key] = [result[key]];
      }
      result[key].push(value);
    } else {
      result[key] = value;
    }
  }

  // Single-element arrays become scalars
  for (const key in result) {
    if (Array.isArray(result[key]) && result[key].length === 1) {
      result[key] = result[key][0];
    }
  }

  return result;
}

Common Use Cases