Find property by key in deep object

findAll.js

// with recursion
function findAll(obj, key){
 if(Array.isArray(obj)){
    return obj.reduce((a,v) => a.concat(findAll(v, key)),[]);
 }
 if(typeof obj === 'object'){
    return Object.keys(obj).reduce(function(v, k){
        if(k === key){
            return v.concat(obj[k]);
        }
        if(typeof obj[k] === 'object'){
            return v.concat(findAll(obj[k], key));
        }
        return v;
    }, [])
 }
 return [];
}
        
// without recursion
function findAll(obj, key) {
var result = [];

 if (!Array.isArray(obj)) {
    obj = [obj];
 }
 for (var i = 0; i < obj.length; i++) {
    if (Array.isArray(obj[i])) {
        obj = obj.concat(obj[i]);
    } else if (typeof obj[i] === "object") {
        Object.keys(obj[i]).forEach(k => {
            if (k === key) {
                result.push(obj[i][k]);
            }
            if (Array.isArray(obj[i][k])) {
                obj = obj.concat(obj[i][k]);
            } else if (typeof obj[i][k] === "object") {
                obj.push(obj[i][k]);
            }
        })
    }
 }

 return result;
}

Needs explicit null check on lines 6 and 30. Also on line 37.

Totally the same with walk-composite library:

import {Walk} from 'walk-composite';
const findAll = (obj, key) => {
    let values = [];
    Walk({
        keysMethod: structure => {
            const value = structure[key];
            if (value !== undefined) {
                values.push(value);
            }
            return Object.keys(structure);
        }
    })(() => {})(obj)
    return values;
}

BTW, null checks are built-in the library: data === null || typeof data !== 'object'