Javascript/JSON get path to given subnode?

Question

How would you get a JSON path to a given child node of an object?

E.g.:

var data = {
    key1: {
        children: {
            key2:'value',
            key3:'value',
            key4: { ... }
        }, 
    key5: 'value'
}

An variable with a reference to key4 is given. Now I'm looking for the absolute path:

data.key1.children.key4

Is there any way to get this done in JS?

Thank you in advance.

Answer 1

So you have a variable with the value "key3", and you want to know how to access this property dynamically, based on the value of this string?

var str = "key3";
data["key1"]["children"][str];

EDIT

Wow, I can't believe I got this on the first try. There might be some bugs in it, but it works for your test case

LIVE DEMO

var x = data.key1.children.key4;

var path = "data";
function search(path, obj, target) {
    for (var k in obj) {
        if (obj.hasOwnProperty(k))
            if (obj[k] === target)
                return path + "['" + k + "']"
            else if (typeof obj[k] === "object") {
                var result = search(path + "['" + k + "']", obj[k], target);
                if (result)
                    return result;
            }
    }
    return false;
}

var path = search(path, data, x);
console.log(path); //data['key1']['children']['key4']

Answer 2

This is the way i have done this.

/**
 * Converts a string path to a value that is existing in a json object.
 * 
 * @param {Object} jsonData Json data to use for searching the value.
 * @param {Object} path the path to use to find the value.
 * @returns {valueOfThePath|null}
 */
function jsonPathToValue(jsonData, path) {
    if (!(jsonData instanceof Object) || typeof (path) === "undefined") {
        throw "Not valid argument:jsonData:" + jsonData + ", path:" + path;
    }
    path = path.replace(/\[(\w+)\]/g, '.$1'); // convert indexes to properties
    path = path.replace(/^\./, ''); // strip a leading dot
    var pathArray = path.split('.');
    for (var i = 0, n = pathArray.length; i < n; ++i) {
        var key = pathArray[i];
        if (key in jsonData) {
            if (jsonData[key] !== null) {
                jsonData = jsonData[key];
            } else {
                return null;
            }
        } else {
            return key;
        }
    }
    return jsonData;
}  

For testing,

var obj = {d1:{d2:"a",d3:{d4:"b",d5:{d6:"c"}}}};
jsonPathToValue(obj, "d1.d2"); // a 
jsonPathToValue(obj, "d1.d3"); // {d4: "b", d5: Object}
jsonPathToValue(obj, "d1.d3.d4"); // b
jsonPathToValue(obj, "d1.d3.d5"); // {d6: "c"}
jsonPathToValue(obj, "d1.d3.d5.d6"); // c

Hope that will help someone.

Answer 3

My solution:

• depth first search based on a given reference
• uses recursion
• handles arrays

(Result can be retrieved using this deep_value function.)

var key4Ref = { abc: 123 }

var data = {
    key1: {
        children: {
            key2:'value',
            key3:'value',
            key4: key4Ref
        }, 
        key5: 'value'
    }
}

// find the path to a 'ref' within an object 'data'.
const pathTo = (ref, data, path = []) => {
  const found = data && Object.entries(data).find(([k,v]) => {
    if (v === ref) return path.push(k)
    if (typeof v === 'object') {
      const tmp = pathTo(ref, v, [...path, k])
      if (tmp) return path = tmp
    }
  })
  if (found) return path
}

console.log(pathTo(key4Ref, data).join('.'))

Answer 4

var data = {
  // Your data is here
  a: {
    b: {
      c: {
        d: "Assalamu alal muslimin"
      }
    }
  },
  // Your function is here
  take: function(path) {
    var temp = this; // take a copy of object
    if(!path) return temp; // if path is undefined or empty return the copy
    path = path.split("/");
    for(var p in path) {
      if(!path[p]) continue; // means "a/" = "a"
      temp = temp[path[p]]; // new data is subdata of data
      if(!temp) return temp; 
    }
    return temp;
  }
};

<input placeholder="Please enter the path"/>
<button onclick="document.querySelector('div').innerText = JSON.stringify(data.take(document.querySelector('input').value))">
  Try it
</button>
<br><br>
Data: {a:{b:{c:{d:"Assalamu alal muslimin"}}}}
<br><br>
Code: data.take(path)
<br><br>
Result:
<div></div>

Shortly the function is :

function getDataByPath(data, path) {
    if(!path) return data; // if path is undefined or empty return data
    path = path.split("/");
    for(var p in path) {
        if(!path[p]) continue; // "a/" = "a"
      . data = data[path[p]]; // new data is subdata of data
        if(!data) return data; // "a/b/d" = undefined
    }
    return data;
}

And the shortest function but it may give errors if you entered wrong path:

function getDataByPath(data, path) {
  for(var i in path.split("/")) data = data[path[i]];
  return data;
}

Answer 5

let x;
try{
  x = JSON.parse(prompt("Input your JSON"))
}
catch(e) {
   alert("not a valid json input")
}
var res = {};
var constructResultCurry = function(src){ return constructResult(res,src); }
        
function constructResult(target, src) {
  if(!src) return;
  target[src.key] = src.val;
}
        
function buildPath(key, obj, overAllKey) {
  overAllKey += (overAllKey ? "." : "") + key;
  if(typeof obj[key] != "object") return { key : overAllKey, val : obj[key] };
  Object.keys(obj[key]).forEach(function(keyInner) {
     constructResultCurry(buildPath(keyInner, obj[key], overAllKey));  
  });
}
        
Object.keys(x).forEach(function(k){
  constructResultCurry(buildPath(k, x, ""));
});
console.log("**************ALL FIELDS****************")
console.log(res);
console.log("******************************************")

let conf = confirm("do you need a specific field from JSON");
if ( conf )
{
   let field = prompt("Input field name")
   let results = Object.fromEntries(
  Object.entries(res).filter(([key]) => (key.toLowerCase()).includes((field.toLowerCase()))))
  prompt("Copy to clipboard: Ctrl+C, Enter", JSON.stringify(results));
   console.log(results)
   
} 
else {
   prompt("Copy to clipboard: Ctrl+C, Enter", JSON.stringify(res));
}

The above solution returns the whole json with a full path to every field in it. And also the path of specific field that was requested.

Answer 6

I'm also trying to solve this problem, the JSON path also include array, and this is the method I finally came up with:

function findValuePath(obj, value) {
    // Initialize the array of results and the array of paths
    let result = [];
    let path = [];

    // Recursive functions look up values
    function searchValue(obj, value) {
        for (let key in obj) {
            // If the current attribute value is equal to the target value, the path is logged
            if (obj[key] === value) {
                path.push((Array.isArray(obj) ? `[${key}]` : `.${key}`));
                result = path.slice();
                path.pop();
            }
            // If the current property is an object or array, search recursively
            else if (typeof obj[key] === 'object') {
                path.push((Array.isArray(obj) ? `[${key}]` : `.${key}`));
                searchValue(obj[key], value);
                path.pop();
            }
        }
    }

    // Call the recursive function
    searchValue(obj, value);

    //If the target value is found, the path string is returned, otherwise an empty string is returned
    return result.length > 0 ? result.join('') : '';
}

This is the test example I made:

let obj = {
    a:1,
    b:"hello",
    c:{
        a:"target000",
        b:"tar",
        c:"target_w",
        d:[
            "target0",
            "target1",
            "target2",
            {
                a:2,
                b:"target"
            }
        ]
    }
}
let res = findValuePath(obj,"target")
console.log(res)                   // ".c.d[3].b"
console.log(`obj${res}`)           // "obj.c.d[3].b"
console.log(eval(`obj${res}`))     // "target"