Functions to read and write on graphs with dotted string keys

example.js

const obj = {
    a: {
        a: 5
    },
    b: {
        a: 8
    }
};

console.log(readGraph(obj, 'a.a')); // 5
console.log(readGraph(obj, 'b.a')); // 8

console.log(writeGraph(obj, 'a.a', 10));
console.log(readGraph(obj, 'a.a')); // 10

console.log(writeGraph(obj, 'a.b', 7));
console.log(readGraph(obj, 'a.b')); // 7

console.log(writeGraph(obj, 'c.a.a', 3));
console.log(readGraph(obj, 'c.a.a')); // 3

console.log(readGraph(obj, 'a')); // { a: 10, b: 7 }

graphs.js

function readGraph(obj, path) {
    const names = path.split('.');

    return names.reduce((prev, name) => {
        if (null === prev
            || typeof prev === 'undefined'
        ) {
            return undefined;
        }

        return prev[name];
    }, obj);
}

function writeGraph(obj, path, value) {
    const names = path.split('.');
    const tip = names.pop();

    obj = names.reduce((prev, name) => {
        if (null === prev[name]
            || typeof prev[name] === 'undefined'
        ) {
            prev[name] = {};
        }

        return prev[name];
    }, obj);

    obj[tip] = value;
}