get.ts

/**
 * Parse a path string (with optional bracket notation) into an array of path segments.
 * Supports both dot notation (a.b.c) and bracket notation (a[0].b, a["key"])
 */
function parsePath(path: string): (string | number)[] {
  if (path === '') {
    return [''];
  }

  const segments: (string | number)[] = [];
  let current = '';
  let i = 0;

  while (i < path.length) {
    const char = path[i];

    if (char === '.') {
      if (current) {
        segments.push(current);
        current = '';
      }
      i++;
      continue;
    }

    if (char === '[') {
      if (current) {
        segments.push(current);
        current = '';
      }
      i++;

      // Check for quoted key
      if (path[i] === '"' || path[i] === "'") {
        const quote = path[i];
        i++;
        let key = '';
        while (i < path.length && path[i] !== quote) {
          key += path[i];
          i++;
        }
        segments.push(key);
        i += 2; // skip closing quote and opening bracket
        continue;
      }

      // Numeric index
      let index = '';
      while (i < path.length && path[i] !== ']') {
        index += path[i];
        i++;
      }
      segments.push(parseInt(index, 10));
      i++; // skip closing bracket
      continue;
    }

    current += char;
    i++;
  }

  if (current) {
    segments.push(current);
  }

  return segments;
}

/**
 * See: https://github.com/angus-c/just/blob/d8c5dd18941062d8db7e9310ecc8f53fd607df54/packages/object-safe-get/index.mjs#L33C1-L61C2
 */
export function get<T = any>(
  obj: any,
  propsArg: string | number | symbol | (string | number | symbol)[],
  defaultValue?: T
): T {
  if (!obj) {
    return defaultValue as T;
  }

  let props: (string | number | symbol)[];

  if (Array.isArray(propsArg)) {
    props = propsArg.slice(0);
  } else if (typeof propsArg === 'string') {
    props = parsePath(propsArg);
  } else if (typeof propsArg === 'symbol') {
    props = [propsArg];
  } else if (typeof propsArg === 'number') {
    props = [propsArg];
  } else {
    throw new Error('props arg must be an array, a string, a number or a symbol');
  }

  let result: any = obj;

  while (props.length) {
    const prop = props.shift()!;
    if (!result) {
      return defaultValue as T;
    }
    result = result[prop];
    if (result === undefined) {
      return defaultValue as T;
    }
  }

  return result;
}