Generate a nested object structure by string key/path

Question

I want to make a function called createAssociativeArray which will recive two parameters: string and object, like this:

function createAssociativeArray(string, object) {
  //...
}

The last item of string should get the object data. See an use/return example:

createAssociativeArray('key1.key2.key3', {
  data1: 1,
  data2: 2,
  data3: 3
});

// key1: {
//   key2: {
//     key3: {
//       data1: 1,
//       data2: 2,
//       data3: 3
//     }
//   }
// }

What's the most simple and robust method to do it?

Use eval isn't is a possibility.

What I was tried:

function createAssociativeArray(string, object) {
  string = string.split('.');
  return string.reduce(function(_object, _target, i) {
    _object[_target] = (i + 1 === string.length ? object : {});
    return _object;
  }, {});
}

It didn't produced the expected result because the object is reseted to {}.

[JSFiddle]

Are you trying to implement namespaces? Also, where does the i variable come from? — user2844991
– user2844991, Commented Sep 25, 2015 at 22:25
@StefanBaiu, something like... It's a index from reduce (updated). — Caio Tarifa
– Caio Tarifa, Commented Sep 25, 2015 at 22:28

user2844991 · Accepted Answer · 2015-09-25 22:39:42Z

5

Here's what I came up with:

function createAssociativeArray(string, object) {
  var parts = string.split('.');
  var last = parts[parts.length - 1];
  var tree = {};

  var node = parts.slice(0, -1).reduce(function (memo, current) {
     return (memo[current] = {});
  }, tree);

  node[last] = object;
  return tree;
}

answered Sep 25, 2015 at 22:39

user2844991

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1 Comment

TechMaze Over a year ago

Try this if you want to merge with an exitsing Object (set the value on a JSON path in a given object): stackoverflow.com/a/32791758/2045312

Maximillian Laumeister · Accepted Answer · 2015-09-25 22:46:09Z

3

I was curious to see if I could make a recursive solution, so here it is:

function createAssociativeArray(string, object) {
    if (string === "") return object;
    var stringarr = string.split('.');
    var laststr = stringarr.pop();
    var newobj = {};
    newobj[laststr] = object;
    return createAssociativeArray(stringarr.join("."), newobj);
}

Working JSFiddle demo: https://jsfiddle.net/pt352dxg/

answered Sep 25, 2015 at 22:46

Maximillian Laumeister

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Comments

letiagoalves · Accepted Answer · 2015-09-25 22:47:17Z

2

Possible implementation:

Working demo

function createChain(keys, value) {
  var obj = {};
  var target = obj;
  keys = keys.split('.');
  keys.forEach(function(key, index) {
    target = target[key] = index === keys.length - 1 ? value : {};
  });
  target = value;
  return obj;
}

answered Sep 25, 2015 at 22:47

letiagoalves

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Comments

TechMaze · Accepted Answer · 2015-09-25 23:04:05Z

This function actually can accept an optional existing Object ({k:2, kk: 3, key1: 4}) and merge that with given json path. e.g. Try on chrome debugger console:

JSON.stringify(createAssociativeArray('key1.key2.key3', {  data1: 1,  data2: 2,  data3: 3}, {k:2,kk:3, key1:{}}))

will print this:

"{"k":2,"kk":3,"key1":{"key2":{"key3":{"data1":1,"data2":2,"data3":3}}}}"

..

  function createAssociativeArray(key, value, data) {
         if(!finalData && data)
           finalData = data;
         var finalData;
         if (!data)
             data = finalData = {};
         var keys = key.split('.');
         if (keys.length < 2) {
           data[keys[0]] = value; 
         } else {
           if (!data[keys[0]])
               data[keys[0]] = {};
           data = data[keys.shift()];              
           createAssociativeArray(keys.join("."),value,data);
         }
         return finalData;
    };

JustcallmeDrago · Accepted Answer · 2015-09-26 03:52:13Z

2

You were pretty close in your original attempt.

function createAssociativeArray(string, object) {
    return string.split('.').reverse().reduce(function (inner, key) {
        var outer = {};
        outer[key] = inner;
        return outer;
    }, object);
}

http://jsfiddle.net/xewoa06t/

answered Sep 26, 2015 at 3:52

JustcallmeDrago

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Comments

Paul G · Accepted Answer · 2015-09-25 22:55:20Z

1

This worked for me:

function createAssociativeArray(string, object){
    var array = string.split('.');
    var aArray = {};
    if(array.length > 1){
         aArray[array[array.length - 1]] = object;
         array.splice(array.length - 1, 1);
         createAssociativeArray(array.join('.'), aArray)
    }else{
        aArray[array[array.length - 1]] = object;
        return aArray
    } 
};


createAssociativeArray('key1.key2.key3', {data1: 1, data2: 2, data3: 3});

Basically, builds object from ground up, starting with the original object, then wrapping the 'layers' around it recursively

answered Sep 25, 2015 at 22:55

Paul G

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Comments

wintvelt · Accepted Answer · 2015-09-25 23:00:00Z

1

Nice case for a recursive function!

function createAssociativeArray(string, object) {
  if (string.split('.').length == 1) {
    var outObj = {};
    outObj[string] = object;
    return outObj;
  } else {
    var outObj = {};
    outObj[string.split('.')[0]] = createAssociativeArray(string.split('.').slice(1).join('.'), object);
    return outObj;
  }
}

answered Sep 25, 2015 at 23:00

wintvelt

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Comments

edc65 · Accepted Answer · 2015-09-26 10:46:18Z

0

It's easier with a simple loop, the key point is doing in reverse (like @JustcallmeDrago)

function createAssociativeArray(keys, data)
{
  var temp, keyPart
  
  for(keys = keys.split('.'); keys.length; data = temp)
  {
    keyPart = keys.pop()
    temp = {}
    temp[keyPart] = data
  }
  return data
}  

// TEST

x = createAssociativeArray("key1.key2.key3", { data1: "value1", data2: "value2" })

document.write('<pre>'+x+'\n'+x.key1 +'\n'
               +x.key1.key2 + '\n'
               +x.key1.key2.key3 +'\n'
               +x.key1.key2.key3.data1 +'\n'
               +x.key1.key2.key3.data2 +'</pre>')

answered Sep 26, 2015 at 10:46

edc65

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Comments

Andreas Louv · Accepted Answer · 2015-09-30 15:24:37Z

0

Since no one have proviced a while-loop solution:

function namespace(path, context) {
    var obj = context;
    var s = path.split('.');
    var p;
    while (s.length) {
        p = s.shift();
        obj = obj[p] || (obj[p] = {});
    }
    return context;
}

answered Sep 30, 2015 at 15:24

Andreas Louv

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Comments

Chris Gunawardena · Accepted Answer · 2018-09-17 21:16:30Z

0

ES6 one liner

(str, obj) => str.split('.').reverse().reduce((inner, key) => ({[key]: inner}), obj);

answered Sep 17, 2018 at 21:16

Chris Gunawardena

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