使用循环创建动态嵌套对象

Question

I wanna create a nested object dynamically. I can create it hard coded. Is it possible to do this with a loop?

result = {}
keys = ["a", "b", "c", "d"]

result[keys[0]] = {}
result[keys[0]][keys[1]] = {}
result[keys[0]][keys[1]][keys[2]] = {}
result[keys[0]][keys[1]][keys[2]][keys[3]] = "cool"

I want to pass an integer for example if it is "3", this should created an object like:

result = {
  "a": {
     "b": {
        "c": "cool"
     }
   }
}

If it is 4, :

result = {
  "a": {
     "b": {
        "c": {
           "d": "cool"
        }
     }
   }
}

So on...

edit:

I am also checking result object, in order to create this nested structure. If there is not any field yet, I simply create the object.

Using this structure to group data. Any chance to check these dynamically?

if (!result[keys[0]]) 
if (!result[keys[0]][keys[1]]) 
if (!result[keys[0]][keys[1]][keys[2]]) 

Answer 1

You can use reduceRight() for this. It just starts from the inside at the last item in the keys list and works its way out starting with "cool":

 let keys = ["a", "b", "c", "d"] let limit = 3 let result = keys.reduceRight((obj, key) => ({[key]: obj}), "cool") console.log(result) 

To limit where the object stops you can iterate over a slice of the keys. For example:

 let keys = ["a", "b", "c", "d"] let start = 0 let stop = 3 // slices are don't inlcude the last item, so this will stop at index 2 let result = keys.slice(start, stop).reduceRight((obj, key) => ({ [key]: obj }), "cool") console.log(result) 

Answer 2

simple for-loop solution.

 let result = {} let keys = ["a", "b", "c", "d"] let depth=3; let current = result for(let i=0;i<depth;++i){ let key = keys[i] if(i == depth-1) current[key] = 'cool' else current = current[key] = {} } console.log(result) 

Answer 3

If you like to add to a given object a new property, you could reduce the keys with the object and take default objects for not given keys. At the end assign the value.

 function setValue(object, path, value, limit) { var keys = path.slice(0, limit), last = keys.pop(); keys.reduce((o, k) => o[k] = o[k] || {}, object)[last] = value; return object; } var result = { foo: 42 }, keys = ["a", "b", "c", "d"]; setValue(result, keys, 'cool'); console.log(result); setValue(result, keys, 'cool', 3); console.log(result); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

Answer 4

I'd use a reducer, along with some basic tests to help me out: https://youtu.be/D6zLI8zrfVs

https://gist.github.com/brianswisher/2ce1ffe3ec08634f78aacd1b7baa31f9

Answer 5

short and simple using reduce

let object1= {}
keys = ['a', 'b', 'c']

keys.reduce((prev,curr,i)=>{
    prev[curr] = {}
    return prev[curr]
}, object1)

log(object1) 
// {
//   a:{
//     b:{
//        c:{}
//     }
//   }
// }