Get object value from string path

Implement a method in Javascript that will take an object and a string or array of strings as a path and return the value at that path. If nothing is found return undefined. Polyfill for lodash._get().

Example

Input:
const obj = {
  a: {
    b: {
      c: [1,2,3]
    }
  }
};

console.log(get(obj, 'a.b.c')); 
console.log(get(obj, 'a.b.c.0')); 
console.log(get(obj, 'a.b.c[1]')); 
console.log(get(obj, 'a.b.c[3]')); 


Output:
// [1,2,3]
// 1
// 2
// undefined

We can implement this method using the following steps.

• Check the type of path, if it is an array of strings, concatenate it and form a string.
• Traverse the string and get the actual values from it ignoring the special characters like [, ], and ..
• Once we have the exact path, deeply traverse the input nested object to find the value.

const get = (obj, path) => {
  // if path is not a string or array of string
  if (path === '' || path.length == 0) return undefined;
  
  // if path is an array, concatenate it and form a string
  // to handle a single case of string
  if (Array.isArray(path)) path = path.join('.');
  
  // filter out the brackets and dot
  let exactPath = [];
  for (let i = 0; i < path.length; i++) {
    if (path[i] !== '[' && path[i] !== ']' && path[i] !== '.') {
      exactPath.push(path[i]);
    }
  }
  
  // get the value of the path in the sequence
  const value = exactPath.reduce((source, path) => source[path], obj);
  
  // if not found return undefined
  return value ? value : undefined;
}

Input:
const obj = {
  a: {
    b: {
      c: [1,2,3]
    }
  }
};

console.log(get(obj, 'a.b.c')); 
console.log(get(obj, 'a.b.c.0')); 
console.log(get(obj, 'a.b.c[1]')); 
console.log(get(obj, ['a', 'b', 'c', '2']));
console.log(get(obj, 'a.b.c[3]'));
console.log(get(obj, 'a.c')); 

Output:
// [1,2,3]
// 1
// 2
// 3
// undefined
// 'undefined'