change string to array

Question

I retrieve the following array of string values

[
"Module1.resource1.create",
"Module1.resource1.read",
"Module1.resource1.update",
"Module1.resource1.delete",
...
"Module1.resourceN.create",
"Module1.resourceN.read",
"Module1.resourceN.update",
]

I would like to change them to json format like this

{"privileges": {
 "Module1": {
 "resource1": {
 "create": true,
 "read": true,
 "update": true,
 "delete": true,
 },
...
 "resourceN": {
 "create": true,
 "read": true,
 "update": true,
 }
 }
 }
}

All I can think of is run a loop for each string, use split(".") and then somehow change it to json object. the problem I'm having is that the json is not a simple key: value, it's more of a key: object: object: object: value if that makes sense ...

I would appreciate the nudge in the right direction.

cheers

• jonatjano: IMO the loop and split is the way to go
• Tomasz Golinski: @jonatjano but not sure how to change the array to multi dimentional json... I can do key: value. but not sure how to do key: object: object: key: value if you know what I mean ...
• zfrisch: are they always going to be in order?
• Tomasz Golinski: @zfrisch - that cannot be guaranteed.

Answer 1

You can use Array#reduce method:

const result = { privileges: {} };
items.reduce((ret, el) => {
 // Split the array elements and use destructuring assignment syntax for
 // creating constants
 const [module, resource, verb] = el.split('.');
 // check if privileges[module] property exists. If not, define it as an empty object.
 if (!ret[module]) ret[module] = {};
 // follows the previous line's logic for resources!
 if (!ret[module][resource]) ret[module][resource] = {};
 ret[module][resource][verb] = true;
 return ret;
}, result.privileges);

Demo | Destructuring assignment syntax

• Tomasz Golinski: that works exactly as I want it to work! thanks. However, I don't really understand what is happening there.. Is it too much to ask for some explanation? I would appreciate that.
• Ram: You are welcome! I'll add some comments to the code.
• Tomasz Golinski: thank you. It's always better to understand than just copy and paste :)
• Tomasz Golinski: interesting. I never knew about Destructuring assignment syntax, this will come in handy :) thanks

Answer 2

May be using dot-object will help without reinventing the wheel:

https://github.com/rhalff/dot-object

• connexo: Good find! Even though I think the question is more about how to achieve that from the coding side.

Answer 3

This took a while, but does the job:

const rules = [
 "Module1.resource1.create",
 "Module1.resource1.read",
 "Module1.resource1.update",
 "Module1.resource1.delete",
 "Module1.resourceN.create",
 "Module1.resourceN.read",
 "Module1.resourceN.update",
 ].map(rule => rule.split('.'));
 
const res = { privileges: {} };
for (const rule of rules) {
 for (i = 0; i < rule.length; i++) {
 switch (i) {
 case 0: 
 res.privileges[rule[0]] = Object.assign({}, res.privileges[rule[0]])
 break;
 case 1:
 res.privileges[rule[0]][rule[1]] = Object.assign({}, res.privileges[rule[0]][rule[1]])
 break;
 case 2:
 res.privileges[rule[0]][rule[1]][rule[2]] = true
 default:
 }
 }
}
console.log(res)

• Tomasz Golinski: thank you for the effort. It indeed works as intended. I have already accepted another answer, though. Sorry. upvoted though! :)

Answer 4

To do that you can use the following function:

function setIn(target, path, value) {
 var chain = String(path).split('.');
 while (chain.length > 0) {
 var field = chain.shift();
 if (chain.length == 0) {
 target[field] = value;
 } else if (field in target && target[field] !== null && typeof target[field] === 'object') {
 target = target[field];
 } else {
 target[field] = {}
 target = target[field];
 }
 }
 return value;
}

And produce the tree:

var tree = { privileges: {} };
for (var i = 0; i < array.length; i += 1)
 setIn(tree.privileges, array[i], true);

Answer 5

You can use Array.reduce() for this to create your nested map. The above example will work for any level of children and will always set the last child to a boolean value.

const arr = ["Module1.resource1.create","Module1.resource1.read","Module1.resource1.update","Module1.resource1.delete","Module1.resourceN.create","Module1.resourceN.read","Module1.resourceN.update","Module2.resourceN.update",];
let result = {privalages:{}};
result.privalages = arr.reduce((o, curr)=>{
 let props = curr.split(".");
 props.reduce((a, prop, index)=> a[prop] = index !== props.length-1 ?(a[prop] || {}) : true,o);
 return o;
},{});
console.log(result);