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

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; }

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

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/

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

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; }

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

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/

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

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

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

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; } }

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

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>')

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

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; }

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

ES6 one liner

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

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