const obj = {
first: { second: { third: 'done'} },
hello: { world: { foo: { bar: 'wrong' } } },
second: { third: 'wrong'}
};
const arr = [ 'first', 'second', 'third' ];
function traverse(obj, arr) {
}
// output = 'done'
Given a first input as a nested object, and a second input as an array containing strings, what is the best way to traverse the nested object based on the path set by the array to output done?
You can reduce the array arr, changing the accumulator to a deeper object at each step.
const obj = {
first: { second: { third: 'done'} },
hello: { world: { foo: { bar: 'wrong' } } },
second: { third: 'wrong'}
};
const arr = [ 'first', 'second', 'third' ];
function traverse(obj, arr) {
return arr.reduce((acc, curr) => acc ? acc[curr] : undefined, obj);
}
console.log(traverse(obj, arr));
console.log(traverse(obj, ['hello', 'world', 'foo']));
console.log(traverse(obj, ['first', 'hello', 'world']));You can use references
ref[key] is an object, change ref to ref[key]Not Foundref has property name same as last variable then return ref[last] else return Not Foundconst obj = { first: { second: { third: 'done'} },hello: { world: { foo: { bar: 'wrong' } } },second: { third: 'wrong'}};
const arr = [ 'first', 'second', 'third' ];
function traverse(obj, arr) {
let ref = obj
let last = arr[arr.length-1]
for(let i=0; i<arr.length-1; i++){
let key = arr[i]
if(typeof ref[key] === 'object'){
ref = ref[key]
} else{
return "Not found"
}
}
return ref.hasOwnProperty(last) ? ref[last] : "Not found"
}
console.log(traverse(obj,arr))
console.log(traverse(obj,['first','third']))
console.log(traverse(obj,['hello','world']))if you want it short and to handle system file path like :
it returns the object if exist and -1 if not
const obj = {
first: { second: { third: 'done'} },
hello: { world: { foo: { bar: 'wrong' } } },
second: { third: 'wrong'}
};
function traverse(obj, path) {
let seq = path.split('/').filter(x => x != '');
seq.map( s => obj = !obj[s] ? -1 : obj[s] );
return obj;
}
console.log(traverse(obj, '/hello/notexist/'));
console.log(traverse(obj, '/hello/world/'));or even shorter with a reduce() instead of a map() :
function traverse(obj, path) {
let seq = path.split('/').filter(x => x != '');
return seq.reduce((acc, curr) => !acc[curr] ? -1 : acc[curr], obj);
}
or a even even shorter :
function traverse(obj, path) {
return path
.split('/')
.filter(Boolean)
.reduce((acc, curr) => acc[curr] ? acc[curr] : -1, obj);
}
const obj = {
first: { second: { third: 'done'} },
hello: { world: { foo: { bar: 'wrong' } } },
second: { third: 'wrong'}
};
const res = traverse(obj, '/hello/world/'); // return {foo:...}
console.log(res);
getmethod provided bylodash. lodash.com/docs/#get