get / set

This pairs the nested reader get with its write counterpart set. get(obj, 'a.b[0].c') safely reads a deep value; set(obj, 'a.b[0].c', v) writes one — creating any missing objects and arrays along the way, so you never have to hand-build the path first.

Implement both. get(obj, path, defaultValue) returns the value at path (a string like 'a.b[0].c' or an array of keys), or defaultValue if any step is missing. set(obj, path, value) writes value at path, building missing containers, and returns the mutated obj.

Signature

function get(obj, path, defaultValue) {} // read; defaultValue if missing
function set(obj, path, value) {}        // write; creates missing containers

Examples

get({ a: { b: [{ c: 7 }] } }, 'a.b[0].c');       // 7
get({ a: 1 }, 'a.b.c', 'fallback');              // 'fallback'

set({}, 'a.b.c', 1);      // { a: { b: { c: 1 } } }  — objects created
set({}, 'a[0].b', 1);     // { a: [{ b: 1 }] }        — array created for [0]

Notes

• Path syntax — dots and brackets: 'a.b[0].c', or an array ['a', 'b', 0, 'c'].
• set creates containers — for a missing step, make an array if the next segment is a numeric index, otherwise a plain object.
• set mutates and returns obj — it writes in place; the return value is the same object for chaining.
• Don't clobber siblings — writing a.c must not disturb an existing a.b.
• get is safe — a missing intermediate returns defaultValue, never throws.