Implement a function get(obj, path, defaultValue) that safely accesses deeply-nested properties in JavaScript objects.

The function should:

• Take in an object, a path (string in dot/bracket notation or an array of keys), and an optional default value.
• Return the value if the path exists, otherwise return the default value.
• Handle both dot notation (a.b.c) and array indexes (a.b[0].c).

Examples

const obj = { a: { b: { c: 3 } } };

get(obj, 'a.b.c'); // 3
get(obj, 'a.b.d', 'default'); // 'default'
get(obj, ['a', 'b', 'c']); // 3
get({ a: { b: [10, 20, { c: 30 }] } }, 'a.b[2].c'); // 30
get(null, 'a.b', 'fallback'); // 'fallback'