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Js how to set an item at a nested index in an empty array [duplicate]

I hope someone can help me with this Javascript.
I have an Object called "Settings" and I would like to write a function that adds new settings to that object.
The new setting's name and value are provided as strings. The string giving the setting's name is then split by the underscores into an array. The new setting should get added to the existing "Settings" object by creating new nested objects with the names given by each part of the array, except the last part which should be a string giving the setting's value. I should then be able to refer to the setting and e.g. alert its value. I can do this in a static way like this...
var Settings = {};
var newSettingName = "Modules_Video_Plugin";
var newSettingValue = "JWPlayer";
var newSettingNameArray = newSettingName.split("_");
Settings[newSettingNameArray[0]] = {};
Settings[newSettingNameArray[0]][newSettingNameArray[1]] = {};
Settings[newSettingNameArray[0]][newSettingNameArray[1]][newSettingNameArray[2]] = newSettingValue;
alert(Settings.Modules.Mediaplayers.Video.Plugin);
... the part that creates the nested objects is doing this ...
Settings["Modules"] = {};
Settings["Modules"]["Video"] = {};
Settings["Modules"]["Video"]["Plugin"] = "JWPlayer";
However, as the number of parts that make up the setting name can vary, e.g. a newSettingName could be "Modules_Floorplan_Image_Src", I'd like to do this dynamically using a function such as...
createSetting (newSettingNameArray, newSettingValue);
function createSetting(setting, value) {
// code to create new setting goes here
}
Can anyone help me work out how to do this dynamically?
I presume there has to be a for...loop in there to itterate through the array, but I haven't been able to work out a way to create the nested objects.
If you've got this far thanks very much for taking the time to read even if you can't help.

Put in a function, short and fast (no recursion).
var createNestedObject = function( base, names ) {
for( var i = 0; i < names.length; i++ ) {
base = base[ names[i] ] = base[ names[i] ] || {};
}
};
// Usage:
createNestedObject( window, ["shapes", "triangle", "points"] );
// Now window.shapes.triangle.points is an empty object, ready to be used.
It skips already existing parts of the hierarchy. Useful if you are not sure whether the hierarchy was already created.
Or:
A fancier version where you can directly assign the value to the last object in the hierarchy, and you can chain function calls because it returns the last object.
// Function: createNestedObject( base, names[, value] )
// base: the object on which to create the hierarchy
// names: an array of strings contaning the names of the objects
// value (optional): if given, will be the last object in the hierarchy
// Returns: the last object in the hierarchy
var createNestedObject = function( base, names, value ) {
// If a value is given, remove the last name and keep it for later:
var lastName = arguments.length === 3 ? names.pop() : false;
// Walk the hierarchy, creating new objects where needed.
// If the lastName was removed, then the last object is not set yet:
for( var i = 0; i < names.length; i++ ) {
base = base[ names[i] ] = base[ names[i] ] || {};
}
// If a value was given, set it to the last name:
if( lastName ) base = base[ lastName ] = value;
// Return the last object in the hierarchy:
return base;
};
// Usages:
createNestedObject( window, ["shapes", "circle"] );
// Now window.shapes.circle is an empty object, ready to be used.
var obj = {}; // Works with any object other that window too
createNestedObject( obj, ["shapes", "rectangle", "width"], 300 );
// Now we have: obj.shapes.rectangle.width === 300
createNestedObject( obj, "shapes.rectangle.height".split('.'), 400 );
// Now we have: obj.shapes.rectangle.height === 400
Note: if your hierarchy needs to be built from values other that standard objects (ie. not {}), see also TimDog's answer below.
Edit: uses regular loops instead of for...in loops. It's safer in cases where a library modifies the Array prototype.

function assign(obj, keyPath, value) {
lastKeyIndex = keyPath.length-1;
for (var i = 0; i < lastKeyIndex; ++ i) {
key = keyPath[i];
if (!(key in obj)){
obj[key] = {}
}
obj = obj[key];
}
obj[keyPath[lastKeyIndex]] = value;
}
Usage:
var settings = {};
assign(settings, ['Modules', 'Video', 'Plugin'], 'JWPlayer');

My ES2015 solution. Keeps existing values.
const set = (obj, path, val) => {
const keys = path.split('.');
const lastKey = keys.pop();
const lastObj = keys.reduce((obj, key) =>
obj[key] = obj[key] || {},
obj);
lastObj[lastKey] = val;
};
Example:
const obj = {'a': {'prop': {'that': 'exists'}}};
set(obj, 'a.very.deep.prop', 'value');
console.log(JSON.stringify(obj));
// {"a":{"prop":{"that":"exists"},"very":{"deep":{"prop":"value"}}}}

Using ES6 is shorten. Set your path into an array.
first, you have to reverse the array, to start filling the object.
let obj = ['a','b','c'] // {a:{b:{c:{}}}
obj.reverse();
const nestedObject = obj.reduce((prev, current) => (
{[current]:{...prev}}
), {});

Another recursive solution:
var nest = function(obj, keys, v) {
if (keys.length === 1) {
obj[keys[0]] = v;
} else {
var key = keys.shift();
obj[key] = nest(typeof obj[key] === 'undefined' ? {} : obj[key], keys, v);
}
return obj;
};
Example usage:
var dog = {bark: {sound: 'bark!'}};
nest(dog, ['bark', 'loudness'], 66);
nest(dog, ['woff', 'sound'], 'woff!');
console.log(dog); // {bark: {loudness: 66, sound: "bark!"}, woff: {sound: "woff!"}}

I love this ES6 immutable way to set certain value on nested field:
const setValueToField = (fields, value) => {
const reducer = (acc, item, index, arr) => ({ [item]: index + 1 < arr.length ? acc : value });
return fields.reduceRight(reducer, {});
};
And then use it with creating your target object.
const targetObject = setValueToField(['one', 'two', 'three'], 'nice');
console.log(targetObject); // Output: { one: { two: { three: 'nice' } } }

Lodash has a _.set method to achieve this
let obj = {}
_.set(obj, ['a', 'b', 'c', 'd'], 'e')
or
_.set(obj, 'a.b.c.d', 'e')
// which generate the following object
{
"a": {
"b": {
"c": {
"d": "e"
}
}
}
}

Here is a simple tweak to jlgrall's answer that allows setting distinct values on each element in the nested hierarchy:
var createNestedObject = function( base, names, values ) {
for( var i in names ) base = base[ names[i] ] = base[ names[i] ] || (values[i] || {});
};
Hope it helps.

Here is a functional solution to dynamically create nested objects.
const nest = (path, obj) => {
const reversedPath = path.split('.').reverse();
const iter = ([head, ...tail], obj) => {
if (!head) {
return obj;
}
const newObj = {[head]: {...obj}};
return iter(tail, newObj);
}
return iter(reversedPath, obj);
}
Example:
const data = {prop: 'someData'};
const path = 'a.deep.path';
const result = nest(path, data);
console.log(JSON.stringify(result));
// {"a":{"deep":{"path":{"prop":"someData"}}}}

Inspired by ImmutableJS setIn method which will never mutate the original. This works with mixed array and object nested values.
function setIn(obj = {}, [prop, ...rest], value) {
const newObj = Array.isArray(obj) ? [...obj] : {...obj};
newObj[prop] = rest.length ? setIn(obj[prop], rest, value) : value;
return newObj;
}
var obj = {
a: {
b: {
c: [
{d: 5}
]
}
}
};
const newObj = setIn(obj, ["a", "b", "c", 0, "x"], "new");
//obj === {a: {b: {c: [{d: 5}]}}}
//newObj === {a: {b: {c: [{d: 5, x: "new"}]}}}

Appreciate that this question is mega old! But after coming across a need to do something like this in node, I made a module and published it to npm.
Nestob
var nestob = require('nestob');
//Create a new nestable object - instead of the standard js object ({})
var newNested = new nestob.Nestable();
//Set nested object properties without having to create the objects first!
newNested.setNested('biscuits.oblong.marmaduke', 'cheese');
newNested.setNested(['orange', 'tartan', 'pipedream'], { poppers: 'astray', numbers: [123,456,789]});
console.log(newNested, newNested.orange.tartan.pipedream);
//{ biscuits: { oblong: { marmaduke: 'cheese' } },
orange: { tartan: { pipedream: [Object] } } } { poppers: 'astray', numbers: [ 123, 456, 789 ] }
//Get nested object properties without having to worry about whether the objects exist
//Pass in a default value to be returned if desired
console.log(newNested.getNested('generic.yoghurt.asguard', 'autodrome'));
//autodrome
//You can also pass in an array containing the object keys
console.log(newNested.getNested(['chosp', 'umbridge', 'dollar'], 'symbols'));
//symbols
//You can also use nestob to modify objects not created using nestob
var normalObj = {};
nestob.setNested(normalObj, 'running.out.of', 'words');
console.log(normalObj);
//{ running: { out: { of: 'words' } } }
console.log(nestob.getNested(normalObj, 'random.things', 'indigo'));
//indigo
console.log(nestob.getNested(normalObj, 'improbable.apricots'));
//false

Inside your loop you can use lodash.set and will create the path for you:
...
const set = require('lodash.set');
const p = {};
const [type, lang, name] = f.split('.');
set(p, [lang, type, name], '');
console.log(p);
// { lang: { 'type': { 'name': '' }}}

try using recursive function:
function createSetting(setting, value, index) {
if (typeof index !== 'number') {
index = 0;
}
if (index+1 == setting.length ) {
settings[setting[index]] = value;
}
else {
settings[setting[index]] = {};
createSetting(setting, value, ++index);
}
}

I think, this is shorter:
Settings = {};
newSettingName = "Modules_Floorplan_Image_Src";
newSettingValue = "JWPlayer";
newSettingNameArray = newSettingName.split("_");
a = Settings;
for (var i = 0 in newSettingNameArray) {
var x = newSettingNameArray[i];
a[x] = i == newSettingNameArray.length-1 ? newSettingValue : {};
a = a[x];
}

I found #jlgrall's answer was great but after simplifying it, it didn't work in Chrome. Here's my fixed should anyone want a lite version:
var callback = 'fn.item1.item2.callbackfunction',
cb = callback.split('.'),
baseObj = window;
function createNestedObject(base, items){
$.each(items, function(i, v){
base = base[v] = (base[v] || {});
});
}
callbackFunction = createNestedObject(baseObj, cb);
console.log(callbackFunction);
I hope this is useful and relevant. Sorry, I've just smashed this example out...

You can define your own Object methods; also I'm using underscore for brevity:
var _ = require('underscore');
// a fast get method for object, by specifying an address with depth
Object.prototype.pick = function(addr) {
if (!_.isArray(addr)) return this[addr]; // if isn't array, just get normally
var tmpo = this;
while (i = addr.shift())
tmpo = tmpo[i];
return tmpo;
};
// a fast set method for object, put value at obj[addr]
Object.prototype.put = function(addr, val) {
if (!_.isArray(addr)) this[addr] = val; // if isn't array, just set normally
this.pick(_.initial(addr))[_.last(addr)] = val;
};
Sample usage:
var obj = {
'foo': {
'bar': 0 }}
obj.pick('foo'); // returns { bar: 0 }
obj.pick(['foo','bar']); // returns 0
obj.put(['foo', 'bar'], -1) // obj becomes {'foo': {'bar': -1}}

A snippet for those who need to create a nested objects with support of array keys to set a value to the end of path. Path is the string like: modal.product.action.review.2.write.survey.data. Based on jlgrall version.
var updateStateQuery = function(state, path, value) {
var names = path.split('.');
for (var i = 0, len = names.length; i < len; i++) {
if (i == (len - 1)) {
state = state[names[i]] = state[names[i]] || value;
}
else if (parseInt(names[i+1]) >= 0) {
state = state[names[i]] = state[names[i]] || [];
}
else {
state = state[names[i]] = state[names[i]] || {};
}
}
};

Set Nested Data:
function setNestedData(root, path, value) {
var paths = path.split('.');
var last_index = paths.length - 1;
paths.forEach(function(key, index) {
if (!(key in root)) root[key] = {};
if (index==last_index) root[key] = value;
root = root[key];
});
return root;
}
var obj = {'existing': 'value'};
setNestedData(obj, 'animal.fish.pet', 'derp');
setNestedData(obj, 'animal.cat.pet', 'musubi');
console.log(JSON.stringify(obj));
// {"existing":"value","animal":{"fish":{"pet":"derp"},"cat":{"pet":"musubi"}}}
Get Nested Data:
function getNestedData(obj, path) {
var index = function(obj, i) { return obj && obj[i]; };
return path.split('.').reduce(index, obj);
}
getNestedData(obj, 'animal.cat.pet')
// "musubi"
getNestedData(obj, 'animal.dog.pet')
// undefined

Try this: https://github.com/silkyland/object-to-formdata
var obj2fd = require('obj2fd/es5').default
var fd = obj2fd({
a:1,
b:[
{c: 3},
{d: 4}
]
})
Result :
fd = [
a => 1,
b => [
c => 3,
d => 4
]
]

Here is a decomposition to several useful functions, that each preserve existing data. Does not handle arrays.
setDeep: Answers question. Non-destructive to other data in the object.
setDefaultDeep: Same, but only sets if not already set.
setDefault: Sets a key if not already set. Same as Python's setdefault.
setStructure: Helper function that builds the path.
// Create a nested structure of objects along path within obj. Only overwrites the final value.
let setDeep = (obj, path, value) =>
setStructure(obj, path.slice(0, -1))[path[path.length - 1]] = value
// Create a nested structure of objects along path within obj. Does not overwrite any value.
let setDefaultDeep = (obj, path, value) =>
setDefault(setStructure(obj, path.slice(0, -1)), path[path.length - 1], value)
// Set obj[key] to value if key is not in object, and return obj[key]
let setDefault = (obj, key, value) =>
obj[key] = key in obj ? obj[key] : value;
// Create a nested structure of objects along path within obj. Does not overwrite any value.
let setStructure = (obj, path) =>
path.reduce((obj, segment) => setDefault(obj, segment, {}), obj);
// EXAMPLES
let temp = {};
// returns the set value, similar to assignment
console.log('temp.a.b.c.d:',
setDeep(temp, ['a', 'b', 'c', 'd'], 'one'))
// not destructive to 'one'
setDeep(temp, ['a', 'b', 'z'], 'two')
// does not overwrite, returns previously set value
console.log('temp.a.b.z: ',
setDefaultDeep(temp, ['a', 'b', 'z'], 'unused'))
// creates new, returns current value
console.log('temp["a.1"]: ',
setDefault(temp, 'a.1', 'three'))
// can also be used as a getter
console.log("temp.x.y.z: ",
setStructure(temp, ['x', 'y', 'z']))
console.log("final object:", temp)
I'm not sure why anyone would want string paths:
They are ambiguous for keys with periods
You have to build the strings in the first place

Since I started with something from this page, I wanted to contribute back
Other examples overwrote the final node even if it was set, and that wasn't what I wanted.
Also, if returnObj is set to true, it returns the base object. By default, falsy, it returns the deepest node.
function param(obj, path, value, returnObj) {
if (typeof path == 'string') path = path.split(".");
var child = obj;
path.forEach((key, i) => {
if (!(key in child)) {
child[key] = (i < path.length-1) ? {} : value || {};
}
child = child[key];
});
return returnObj ? obj : child;
}
var x = {};
var xOut = param(x, "y.z", "setting")
console.log(xOut);
xOut = param(x, "y.z", "overwrite") // won't set
console.log(xOut);
xOut = param(x, "y.a", "setting2")
console.log(xOut);
xOut = param(x, "y.a", "setting2", true) // get object rather than deepest node.
console.log(xOut);
You can also do something where numeric keys are placed in arrays (if they don't already exist). Note that numeric keys won't convert to arrays for the first element of the path, since that's set by the type of your base-object.
function isNumber(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}
function param(obj, path, value, returnObj) {
if (typeof path == 'string') path = path.split(".");
var child = obj;
path.forEach((key, i) => {
var nextKey = path[i+1];
if (!(key in child)) {
child[key] = (nextKey == undefined && value != undefined
? value
: isNumber(nextKey)
? []
: {});
}
child = child[key];
});
return returnObj ? obj : child;
}
var x = {};
var xOut = param(x, "y.z", "setting")
console.log(xOut);
xOut = param(x, "y.z", "overwrite") // won't set
console.log(xOut);
xOut = param(x, "y.a", "setting2")
console.log(xOut);
xOut = param(x, "y.a", "setting2", true) // get object rather than deepest node.
xOut = param(x, "1.0.2.a", "setting")
xOut = param(x, "1.0.1.a", "try to override") // won't set
xOut = param(x, "1.0.5.a", "new-setting", true) // get object rather than deepest node.
console.log(xOut);
Naturally, when the numeric keys are greater than 0, you might see some undefined gaps.
Practical uses of this might be
function AddNote(book, page, line) {
// assume a global global notes collection
var myNotes = param(allNotes, [book, page, line], []);
myNotes.push('This was a great twist!')
return myNotes;
}
var allNotes = {}
var youthfulHopes = AddNote('A Game of Thrones', 4, 2, "I'm already hooked, at least I won't have to wait long for the books to come out!");
console.log(allNotes)
// {"A Game of Thrones": [undefined, undefined, undefined, undefined, [undefined, undefined, ["I'm already hooked, at least I won't have to wait long for the books to come out!"]]]}
console.log(youthfulHopes)
// ["I'm already hooked, at least I won't have to wait long for the books to come out!"]

function initPath(obj, path) {
path.split('.').reduce((o, key) => (
Object.assign(o, {[key]: Object(o[key])}),
o[key]
), obj);
return obj;
}
Usage
const obj = { a: { b: 'value1' } };
initPath(obj, 'a.c.d').a.c.d='value2';
/*
{
"a": {
"b": "value1",
"c": {
"d": "value2"
}
}
}
*/

simple answer. on es6, im using this
const assign = (obj, path, value) => {
let keyPath = path.split('.')
let lastKeyIndex = keyPath.length - 1
for (let i = 0; i < lastKeyIndex; ++i) {
let key = keyPath[i]
if (!(key in obj)) {
obj[key] = {}
}
obj = obj[key]
}
obj[keyPath[lastKeyIndex]] = value
}
example json
const obj = {
b: 'hello'
}
you can add new key
assign(obj, 'c.d.e', 'this value')
and you get like bellow
console.log(obj)
//response example
obj = {
b: 'hello',
c: {
d: {
e: 'this value'
}
}
}

function createObj(keys, value) {
let obj = {}
let schema = obj
keys = keys.split('.')
for (let i = 0; i < keys.length - 1; i++) {
schema[keys[i]] = {}
schema = schema[keys[i]]
}
schema[keys.pop()] = value
return obj
}
let keys = 'value1.value2.value3'
let value = 'Hello'
let obj = createObj(keys, value)

Eval is probably overkill but the result is simple to visualize, with no nested loops or recursion.
function buildDir(obj, path){
var paths = path.split('_');
var final = paths.pop();
for (let i = 1; i <= paths.length; i++) {
var key = "obj['" + paths.slice(0, i).join("']['") + "']"
console.log(key)
eval(`${key} = {}`)
}
eval(`${key} = '${final}'`)
return obj
}
var newSettingName = "Modules_Video_Plugin_JWPlayer";
var Settings = buildDir( {}, newSettingName );
Basically you are progressively writing a string "obj['one']= {}", "obj['one']['two']"= {} and evaling it;

find value (and key) of an object in array (JS)

I am writing a function that will iterate through an of objects to find if key:value pair exists and if so, it adds into another array (in case there are multiple matches)
The array contains objects. The function takes as argument what key and value you're looking for and then iterates through array till it finds it. As you can see, key is a variable then and my problem is I am not sure how to access object property when referring to as a variable value.
for (let i = 0; i < arr.length; i++) {
if (arr[i].[key] == value) {
result.push(arr[i]);
}
}
I thought maybe putting it in [key] would help, but I was obviously wrong. I tried googling how to do it, but I guess i can't put it in words right .

You are confusing dot notation with bracket notation.
Remove the .; arr[i].[key] == value1 should be arr[i][key] == value.
const arr = [{
'a': 'b'
}]
key = 'a'
value = 'b'
const result = []
for (let i = 0; i < arr.length; i++) {
if (arr[i][key] == value) {
result.push(arr[i]);
}
}
console.log(result)
You can simplify the code by using filter:
const arr = [{
'a': 'b'
}]
key = 'a'
value = 'b'
const result = arr.filter(e => e[key] == value)
console.log(result)

You can use ES6+ and ternary true ( && == only true action )
const arr = [{
a: 'b'
}];
const key = 'a';
const value = 'b';
const result = [];
for (const item of arr) {
(item[key] === value) && result.push(item)
};
console.log(result);
You can simplify the code by using filter:
const arr = [{
a: 'b'
}];
const key = 'a';
const value = 'b';
const result = [];
for( const item of arr ) {
( item[key] === value ) && result.push( item )
};
console.log( result );

use Array.prototype.filter()
You should know upfront what exact property name you're willing to reference to:
const arr = [
{name:"Evan", age:28},
{name:"John", age:23},
{name:"Anne", age:28},
];
const searchProp = "age";
const searchValue = 28;
const result = arr.filter((user) => user[searchProp] === searchValue);
console.log(result)

You are almost there, just get rid of the extra . between [i] and [key]:
for (let i = 0; i < arr.length; i++) {
if (arr[i][key] == value) {
result.push(arr[i]);
}
}
However, there would be a simpler and more straight-forward way, using filter:
const result = arr.filter(obj => obj[key] == value)
Example:
const arr = [
{ a: 1, b: 1 },
{ a: 1, b: 2 },
{ a: 2, b: 1 },
{ a: 2, b: 2 }
]
const key = 'b'
const value = 1
const result = arr.filter(obj => obj[key] == value)
console.log(result)
// Output: [{ a: 1, b: 1 }, { a: 2, b: 1 }]

How can I use data deep inside Json? [duplicate]

I'm trying to build a function that would expand an object like :
{
'ab.cd.e' : 'foo',
'ab.cd.f' : 'bar',
'ab.g' : 'foo2'
}
Into a nested object :
{ab: {cd: {e:'foo', f:'bar'}, g:'foo2'}}
Like this php function : Set::expand()
Without using eval of course.

I believe this is what you're after:
function deepen(obj) {
const result = {};
// For each object path (property key) in the object
for (const objectPath in obj) {
// Split path into component parts
const parts = objectPath.split('.');
// Create sub-objects along path as needed
let target = result;
while (parts.length > 1) {
const part = parts.shift();
target = target[part] = target[part] || {};
}
// Set value at end of path
target[parts[0]] = obj[objectPath]
}
return result;
}
// For example ...
console.log(deepen({
'ab.cd.e': 'foo',
'ab.cd.f': 'bar',
'ab.g': 'foo2'
}));

If you're using Node.js (e.g. - if not cut and paste out of our module), try this package: https://www.npmjs.org/package/dataobject-parser
Built a module that does the forward/reverse operations:
https://github.com/Gigzolo/dataobject-parser
It's designed as a self managed object right now. Used by instantiating an instance of DataObjectParser.
var structured = DataObjectParser.transpose({
'ab.cd.e' : 'foo',
'ab.cd.f' : 'bar',
'ab.g' : 'foo2'
});
structured.data() returns your nested object:
{ab: {cd: {e:'foo', f:'bar'}, g:'foo2'}}
So here's a working example in JSFiddle:
http://jsfiddle.net/H8Cqx/

Function name is terrible and the code was quickly made, but it should work. Note that this modifies the original object, I am not sure if you wanted to create a new object that is expanded version of the old one.
(function(){
function parseDotNotation( str, val, obj ){
var currentObj = obj,
keys = str.split("."), i, l = keys.length - 1, key;
for( i = 0; i < l; ++i ) {
key = keys[i];
currentObj[key] = currentObj[key] || {};
currentObj = currentObj[key];
}
currentObj[keys[i]] = val;
delete obj[str];
}
Object.expand = function( obj ) {
for( var key in obj ) {
parseDotNotation( key, obj[key], obj );
}
return obj;
};
})();
var expanded = Object.expand({
'ab.cd.e' : 'foo',
'ab.cd.f' : 'bar',
'ab.g' : 'foo2'
});
JSON.stringify( expanded );
//"{"ab":{"cd":{"e":"foo","f":"bar"},"g":"foo2"}}"

Derived from Esailija's answer, with fixes to support multiple top-level keys.
(function () {
function parseDotNotation(str, val, obj) {
var currentObj = obj,
keys = str.split("."),
i, l = Math.max(1, keys.length - 1),
key;
for (i = 0; i < l; ++i) {
key = keys[i];
currentObj[key] = currentObj[key] || {};
currentObj = currentObj[key];
}
currentObj[keys[i]] = val;
delete obj[str];
}
Object.expand = function (obj) {
for (var key in obj) {
if (key.indexOf(".") !== -1)
{
parseDotNotation(key, obj[key], obj);
}
}
return obj;
};
})();
var obj = {
"pizza": "that",
"this.other": "that",
"alphabets": [1, 2, 3, 4],
"this.thing.that": "this"
}
Outputs:
{
"pizza": "that",
"alphabets": [
1,
2,
3,
4
],
"this": {
"other": "that",
"thing": {
"that": "this"
}
}
}
Fiddle

You could split the key string as path and reduce it for assigning the value by using a default object for unvisited levels.
function setValue(object, path, value) {
var keys = path.split('.'),
last = keys.pop();
keys.reduce((o, k) => o[k] = o[k] || {}, object)[last] = value;
return object;
}
var source = { 'ab.cd.e': 'foo', 'ab.cd.f': 'bar', 'ab.g': 'foo2' },
target = Object
.entries(source)
.reduce((o, [k, v]) => setValue(o, k, v), {});
console.log(target);

You need to convert each string key into object. Using following function you can get desire result.
function convertIntoJSON(obj) {
var o = {}, j, d;
for (var m in obj) {
d = m.split(".");
var startOfObj = o;
for (j = 0; j < d.length ; j += 1) {
if (j == d.length - 1) {
startOfObj[d[j]] = obj[m];
}
else {
startOfObj[d[j]] = startOfObj[d[j]] || {};
startOfObj = startOfObj[d[j]];
}
}
}
return o;
}
Now call this function
var aa = {
'ab.cd.e': 'foo',
'ab.cd.f': 'bar',
'ab.g': 'foo2'
};
var desiredObj = convertIntoJSON(aa);

Something that works, but is probably not the most efficient way to do so (also relies on ECMA 5 Object.keys() method, but that can be easily replaced.
var input = {
'ab.cd.e': 'foo',
'ab.cd.f': 'bar',
'ab.g': 'foo2'
};
function createObjects(parent, chainArray, value) {
if (chainArray.length == 1) {
parent[chainArray[0]] = value;
return parent;
}
else {
parent[chainArray[0]] = parent[chainArray[0]] || {};
return createObjects(parent[chainArray[0]], chainArray.slice(1, chainArray.length), value);
}
}
var keys = Object.keys(input);
var result = {};
for(var i = 0, l = keys.length; i < l; i++)
{
createObjects(result, keys[i].split('.'), input[keys[i]]);
}
JSFiddle is here.

Here is how I do this in one of my applications:
const obj = {
"start.headline": "1 headline",
"start.subHeadline": "subHeadline",
"start.accordion.headline": "2 headline",
"start.accordion.sections.0.content": "content 0",
"start.accordion.sections.0.iconName": "icon 0",
"start.accordion.sections.1.headline": "headline 1",
"start.accordion.sections.1.content": "content 1",
"start.accordion.sections.1.iconName": "icon 1",
"start.accordion.sections.2.headline": "headline 2",
"start.accordion.sections.2.content": "content 2",
"start.accordion.sections.2.iconName": "icon 2",
"end.field": "add headline",
"end.button": "add button",
"end.msgs.success": "success msg",
"end.msgs.error": "error msg",
};
const res = Object.keys(obj).reduce((res, key) => {
const path = key.split('.');
const lastIndex = path.length - 1;
path.reduce(
(acc, k, i, a) => acc[k] = lastIndex === i ?
obj[key] :
acc[k] || (/\d/.test(a[i+1]) ? [] : {}),
res
);
return res;
}, {});
console.log(res);

This is the answer as provided by #broofa, but converted to TypeScript.
type NestedObject = { [key: string]: any };
function objectify(obj: NestedObject): NestedObject {
const result: NestedObject = {};
for (const key in obj) {
let target: NestedObject = result;
const parts = key.split(".");
for (let j = 0; j < parts.length - 1; j++) {
const part = parts[j];
target = target[part] = target[part] || {};
}
target[parts[parts.length - 1]] = obj[key];
}
return result;
}

Javascript - Moving occurrences of undefined to the end of an array

I'm looking to move all occurrences of undefined to the end of an array.
So for example if my array looks like: [undefined,"bbc", "cnn"] the function will create: ["bbc", "cnn", undefined]
I have built a script that can do that:
arr = [undefined,"bbc", "cnn"]
var loopNo = 0
for (var f = 0; f < arr.length; f++) {
loopNo += 1
var keyNo = loopNo - 1
if (arr[f] === undefined){
arr.push(arr.splice(keyNo, 1)[0]);
}
}
console.log(arr)
However if undefined occurs more than once it doesn't move it - i.e [undefined , undefined, "cnn"]
How do I make it so undefined is shifted to the end of the array every-time?
Thanks.

Better way [Big O(N)]:
const shiftUndefined = (arr) => {
let duplicate = [];
for (let i = 0, len = arr.length, j = len - 1, k = 0; k <= j; i++) {
const item = arr[i];
if (item === undefined) {
duplicate[j--] = undefined;
} else {
duplicate[k++] = item;
}
}
return duplicate;
};
const arr = [undefined, "bbc", "cnn"];
const arr2 = [undefined, undefined, "cnn"];
console.log(shiftUndefined(arr)); // [ 'bbc', 'cnn', undefined ]
console.log(shiftUndefined(arr2)); // [ 'cnn', undefined, undefined ]
Keep Same ref: Big O(N)
function sameRefMove(array) {
const filtered = array.filter(Boolean);
let index = 0;
while (index < filtered.length) {
array[index] = filtered[index++];
}
while (index < array.length) {
array[index++] = undefined;
}
return array;
}
var array = [undefined, "bbc", "cnn"];
console.log(sameRefMove(array));
console.log(sameRefMove([undefined, undefined, "cnn"]));
Using reduce:
const move = (arr) => {
const [filtered, noValue] = arr.reduce(
([filtered, noValue], item) => {
if (item === undefined) noValue.push(undefined);
else filtered.push(item);
return [filtered, noValue];
},
[[], []]
);
return filtered.concat(noValue);
};
let arr = [undefined, "bbc", "cnn"];
arr = move(arr);
console.log(arr);
arr = [undefined, undefined, "cnn"];
arr = move(arr);
console.log(arr);
Just use sort if performance is not concern.
const arr = [undefined,"bbc", "cnn"]
console.log(arr.sort()) // [ 'bbc', 'cnn', undefined ]

Assuming you:
only want to move undefined to the end of an array without affecting others,
are okay with creating intermediate arrays,
here's a simple way to accomplish this, using Array.prototype.filter():
let arr = [undefined, undefined,"bbc", "cnn", "abc"];
const arrDefined = arr.filter(el => el !== undefined);
const arrUndefined = arr.filter(el => el === undefined);
arr = [...arrDefined, ...arrUndefined];
console.log('arr:', arr);
// [ "bbc", "cnn", "abc", undefined, undefined ]

You could iterate from the end and splice and push undefined values.
function move(value, array) {
var i = array.length - 1;
while (i--) {
if (array[i] === value) {
array.push(array.splice(i, 1)[0]);
}
}
return array;
}
var array = [undefined, "bbc", "cnn"];
console.log(move(undefined, array));

Convert String Into Delimited Object Key

I am trying to convert a string into a delimited object key but I need some assistance on how to iterate over the length of the array and join accordingly.
SET('my.delimited.string.of.unknown.length')
const SET = key => (state, val) => {
if(key.indexOf('.') !== -1) {
let array = key.split(".")
for (var i = 0; i < array.length; i++) {
// what should I do here?
}
// desired output based on array length
// state[ array[0] ][ array[1] ] = val
// state.my.delimited.string.of.unknown.length = val
}
}

One of those very rare usecases for reduce:
const keys = key.split(".");
const prop = keys.pop();
keys.reduce((acc, key) => acc[key], state)[prop] = val;
For sure that could also be done with a for loop:
let array = key.split("."), acc = state;
for (var i = 0; i < array.length - 1; i++) {
acc = acc[ array[i] ];
}
acc[ array.pop() ] = val;

For setting a value, you could split the path and reduce the path by walking the given object. If no object exist, create a new property with the name. Later assign the value.
function setValue(object, path, value) {
var keys = path.split('.'),
last = keys.pop();
keys.reduce((o, k) => o[k] = o[k] || {}, object)[last] = value;
}
var test = {};
setValue(test, "first.deep.property", 1);
setValue(test, "and.another.deep.property", 20);
console.log(test);

You could also do this with a single Array.reduce:
const makeObject = (arr, val, obj={}) => {
arr.split('.').reduce((r,c,i,a) => r[c] = i == a.length-1 ? val : {}, obj)
return obj
}
console.log(makeObject("first.deep.property", 1))
console.log(makeObject("and.another.deep.property", 20))