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Shorthand to manipulate an object attribute and reassign

I have a deeply nested object and I want to manipulate a value of it and reassign it again. Is there a shorthand way for this other than writing it all out again or assigning it to a variable:
createStops[idx]['place']['create'][stop][key][value] = createStops[idx]['place']['create'][stop][key][value].toString()
looks ugly doesn't it? Something like:
createStops[idx]['place']['create'][stop][key][value].toStringAndReassign()
but JS built in.
Edit: In my case it is a number, if it's for your case too please check out #MarkMeyer answer.

No, there isn't.
Assigning a new value requires an assignment.
Strings are immutable, so you can't convert an existing value into a string in-place.

Given a value that's a number, if you just want it to be a string, you can coerce to a string with an assignment operator:
let o = {
akey: {
akey:{
value: 15
}
}
}
o.akey.akey.value += ''
console.log(o)

No,
Going to the same index is needed to store the value

Although it is not possible as mentioned by #Quentin you can define a custom getter in your object like:
var foo = {
a: 5,
b: 6,
get c () {
return this.b.toString()+' text'
}
};
console.log(foo.c);
You're not reassigning the value as you are semantically formatting your values. In order to format your value you are mutating your initial object. If you do not pretend to modify an object for formatting purposes that will work just fine.

You do not have integrated functions to use like that, but you could use of some utilitary functions of your own to help you manage assignements and make it less verbal.
SPOIL : The final use look like
// call the function to do +1 at the specified key
executeFunctionAtKey(
// The object to change the value on
createStops,
// The path
`${idx}.place.create.${stop}.${key}.${value}`,
// The thing to do
(x) => x + 1,
);
const createStops = {
idx: {
place: {
create: {
stop: {
key: {
value: 5,
},
},
},
},
},
};
const idx = 'idx';
const stop = 'stop';
const key = 'key';
const value = 'value';
// Function that go to the specified key and
// execute a function on it.
// The new value is the result of the func
// You can do your toString there, or anything else
function executeFunctionAtKey(obj, path, func) {
const keys = path.split('.');
if (keys.length === 1) {
obj[path] = func(obj[key]);
return obj;
}
const lastPtr = keys.slice(0, keys.length - 1).reduce((tmp, x) => tmp[x], obj);
lastPtr[keys[keys.length - 1]] = func(lastPtr[keys[keys.length - 1]]);
return obj;
}
// call the function to do +1 at the specified key
executeFunctionAtKey(
// The object to change the value on
createStops,
// The path
`${idx}.place.create.${stop}.${key}.${value}`,
// The thing to do
(x) => x + 1,
);
console.log(createStops);
with the toString example from Number to String
const createStops = {
idx: {
place: {
create: {
stop: {
key: {
value: 5,
},
},
},
},
},
};
const idx = 'idx';
const stop = 'stop';
const key = 'key';
const value = 'value';
// Function that go to the specified key and
// execute a function on it.
// The new value is the result of the func
// You can do your toString there, or anything else
function executeFunctionAtKey(obj, path, func) {
const keys = path.split('.');
if (keys.length === 1) {
obj[path] = func(obj[key]);
return obj;
}
const lastPtr = keys.slice(0, keys.length - 1).reduce((tmp, x) => tmp[x], obj);
lastPtr[keys[keys.length - 1]] = func(lastPtr[keys[keys.length - 1]]);
return obj;
}
// call the function to do +1 at the specified key
executeFunctionAtKey(
// The object to change the value on
createStops,
// The path
`${idx}.place.create.${stop}.${key}.${value}`,
// The thing to do
(x) => x.toString(),
);
console.log(createStops);

Theoretically you could build a function that takes an object, a path and the property to set it to.
This will reduce the readability of your code, so i would advice using ordinary assignment. But if you need it check out the snippet below:
//
function setProp(object, path, val) {
var parts = path.split("/").filter(function (p) { return p.length > 0; });
var pathIndex = 0;
var currentTarget = object;
while (pathIndex < parts.length - 1) {
currentTarget = currentTarget[parts[pathIndex]];
pathIndex++;
}
if (val instanceof Function) {
currentTarget[parts[pathIndex]] = val(currentTarget[parts[pathIndex]]);
}
else {
currentTarget[parts[pathIndex]] = val;
}
return object;
}
var createStops = {
idx: {
place: {
create: {
stop: {
key: {
value: 5
}
}
}
}
}
};
function toString(p) { return p.toString(); }
console.log(JSON.stringify(createStops, null, 4));
setProp(createStops, 'idx/place/create/stop/key/value', toString);
console.log(JSON.stringify(createStops, null, 4));
UPDATE 1
Allowed passing functions and used OP JSON structure for snippet

Why is it behaving this way? [duplicate]

This question already has answers here:
Why does map() return an array with undefined values?
(1 answer)
Why does having [].map with curly brackets change the way it works?
(4 answers)
Closed 4 years ago.
When is run this, its printing undefined. while doing the ret.push(func(arr[i])) it does have the context right ?
function print(arr,func){
var ret =[]
for(let i =0 ;i<arr.length;i++){
ret.push(func(arr[i]))
}
return ret;
}
var numbers = [1,2,3,4,5];
console.log(print(numbers,(x)=>{x+1}));
it prints [undefined,undefined,undefined,undefined,undefined].

You could take a return statement and get the new values.
function print(arr, func) {
var ret = [];
for (let i = 0; i < arr.length; i++) {
ret.push(func(arr[i]));
}
return ret;
}
var numbers = [1, 2, 3, 4, 5];
console.log(print(numbers, (x) => { return x + 1; }));
// ^^^^^^
// or take a simplified lambda with implicit return (kudos paul!)
console.log(print(numbers, x => x + 1));

Set JSON property with fully qualified string

This question achieves kinda the opposite of what I'm trying to do. Basically, I have this object:
var a = {
b: {
c: 'Foo'
}
}
What I need to do is set the value of c given the string 'b.c'. Unfortunately, I can't do this:
a['b.c'] = 'Bar'
As far as I can tell, the question above doesn't get me anywhere close as it just copies the values of the object properties so they can be read. It doesn't help me set the values of the object properties, however. Here's what I have so far:
var key = 'b.c'.split('.');
for (var i = 0; i < key.length; i++) {
// do something
}

Here's a functional way, is this what you need? It doesn't use the particular a[string] syntax but a function where you can pass the object string and the value to set:
var obj = { foo: { bar: { lol: { lulz: 69 } } } };
function setProp(obj, prop, value) {
var props = prop.split('.');
return [obj].concat(props).reduce(function(a,b,i) {
return i == props.length ? a[b] = value : a[b];
});
}
setProp(obj, 'foo.bar.lol.lulz', 'hello world');
console.log(obj.foo.bar.lol.lulz); //=> "hello world"

You have to intercept the last iteration of the loop, and from there assign instead of redefining your temp variable.
I adapted the answer to the question you linked to assign the value 2 to a.b.c:
var a = {
"b" : {
"c" : 1
}
}
var n = "b.c".split(".");
var x = a;
for(var i = 0; i < n.length; i++){
if(i == n.length-1) {
x[n[i]] = 2;
} else {
x = x[n[i]];
}
}
http://jsfiddle.net/Fuhbb/
This is pretty much what #Ian is doing in his jsfiddle. Intead of an if, he loops one step less, then deals with the assignment after the loop.

For the record, I eventually figured out another way to do this:
function setProperty(obj, props, val) {
if (obj[props[0]] instanceof Object) {
setProperty(obj[props[0]], props.slice(1, props.length), val);
return;
}
obj[props[0]] = val;
}
Call it like this:
a = {
b: {
c: 'Foo'
}
};
var whatever = 'b.c';
var props = whatever.split('.');
setProperty(a, props, 'Bar');

How to in JavaScript or ExtJS: obj['a.b.c'] = 123 => obj.a.b.c = 123? [duplicate]

This question already has answers here:
Accessing nested JavaScript objects and arrays by string path
(44 answers)
Closed 9 years ago.
I need to convert an object with cannonical properties into object with nested properties, splited by '.'
Example:
From:
obj['a.b.c'] = 123;
to:
obj.a.b.c = 123;
Any elegant solutions?
Or maybe there is a solution in ExtJS to make form.getValues() to return an array of fields grouped by names like fieldname[1] or fieldname.1?

Have a look at the private method in ClassManager "createNamespaces". It's essentially what you need to do, except root shouldn't default to global, it should default to your object:
function setValue(o, key, value) {
var root = o,
parts = key.split('.'),
ln = parts.length,
part, i;
for (i = 0; i < ln; i++) {
part = parts[i];
if (typeof part != 'string') {
root = part;
} else {
if (!root[part]) {
root[part] = (i === ln - 1) ? value : {};
}
root = root[part];
}
}
}
var o = {};
setValue(o, 'a.b.c', 123);
console.log(o.a.b.c);

Concatenate to access an object property [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Dynamic object property name
I want to dynamically generate access to an object's property.
If I try to access mydata[i].val.name I get somename.
If I try it like mydata[i] + bar[j] (where bar[j] === '.val.name') it fails.
How do I dynamically create something like this? So that I can access any property of an object using a user generated value?
Some code:
If I have an object I want to be able to iterate through its properties, gathering the ones I am interested in. Ideally I would like something like the following:
var processData = function (data, keys, values) {
var returnData = [], i, j, k;
var parsedData = JSON.parse(data);
var keys = keys || null;
var values = values || null;
var datalen = parsedData.length;
for (i = 0; i < datalen; i++) {
returnData[i] = {};
for(j = 0; j< keys.length; j++){
for(k = 0; k < values.length; k++){
returnData[i][keys[j]] = parsedData[i] + values;
}
}
}
return returnData;
};
and then use it like:
var keys = ["foo","bar"];
var values = [".val.name", ".val.date"];
processData(data, keys, values);
But this does not work and in console I see foo="[object Object].val.name" rather than the expected foo="ACME Industries".

If you want to stick to your pattern of constructing the subscript as a string with dots in it you have to roll your own lookup function, like so:
function descend(object, sub) {
var handle = object,
stack = sub.split('.'),
history = [],
peek;
while (handle[stack[0]]) {
if (peek) {
history.push(peek);
}
peek = stack.shift();
handle = handle[peek];
}
if (stack.length > 0) {
history.push(peek);
throw "Traversal error, could not descend to '" + stack.join('.') + "' from '" + history.join('.') + "'.";
}
return handle;
}
var x = {
a: {
b: {
c: 15
},
d: 4
}
};
console.log(descend(x, "a"));
console.log(descend(x, "a.b"));
console.log(descend(x, "a.b.c"));
console.log(descend(x, "a.d"));
function processData(data, keys, values) {
if (keys.length !== values.length) {
throw "Mismatched keys and value lookups";
}
var i,
len = keys.length,
gathered = {},
k,
scratch,
v;
for (i = 0; i < len; i += 1) {
k = descend(data, keys[i]);
scratch = values[i].split('.');
scratch.shift();
v = descend(k, scratch.join('.'));
gathered[keys[i]] = v;
}
return gathered;
}
var data = {
foo: {
val: {
name: "ACME Industries"
}
},
bar: {
val: {
date: (new Date())
}
}
};
var keys = ["foo","bar"];
var values = [".val.name", ".val.date"];
processData(data, keys, values);
Please note: this will not be nearly as performant as coding without this style of lookup.

If you try:
new Object() + '.john.doe'
It will concatenate as a string, so you’ll get "[object Object].john.doe".
You should create a function that can handle dynamic property names instead (and there are plenty of those). You also might want to loose the ".foo.bar" syntax as a string (unless you plan to use eval()) and work solely with arrays instead.

If I understand correctly you need to use
mydata[i]["val"]["name"]
So, I'd use something like this:
var result =getItemByValuesPath(myData[i],values);
alert(result);
function getItemByValuesPath(item, values)
{
var result = item;
var vals = values.split(".");
for(var j=0; j<values.length; j++)
{
if(result==undefined)
{
return null;
}
result = result[values[j]];
}
}