#496 JSON.parse

Implement your own version of JSON.parse() that converts JSON strings back to JavaScript values. This is the counterpart to JSON.stringify() and involves parsing various JSON data types.

Requirements

1. Basic types – null, boolean, number, string
2. Arrays – handle nested arrays and mixed types
3. Objects – handle nested objects with string keys
4. String parsing – handle escape sequences, Unicode, quotes
5. Number parsing – handle integers, decimals, scientific notation
6. Whitespace handling – ignore whitespace between tokens
7. Error handling – throw syntax errors for invalid JSON

Key Behaviors

• String escape sequences – \", \\, \/, \b, \f, \n, \r, \t, \uXXXX
• Number formats – 123, 123.45, -123, 1.23e+4, 1.23E-4
• Array parsing – [1, 2, 3], ["a", "b", "c"], [1, [2, 3]]
• Object parsing – {"key": "value"}, nested objects
• Whitespace – ignore spaces, tabs, newlines between tokens
• Error cases – malformed JSON, trailing commas, invalid escapes

Example

parse('{"name": "John", "age": 30}');
// { name: "John", age: 30 }

parse('[1, 2, [3, 4]]');
// [1, 2, [3, 4]]

parse('"Hello\\nWorld"');
// "Hello\nWorld"

parse('123.45e-2');
// 1.2345

parse('{"a": true, "b": null}');
// { a: true, b: null }

Signature

function parse(json: string): any;

Constraints

• Cannot use native JSON.parse() – must implement from scratch
• Handle escape sequences – properly decode string escapes
• Validate JSON syntax – throw errors for invalid input