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'
