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Comparing 2 nested data-structures,target+source,what are appropriate merge-strategies for missing target values compared to their source counterpart?

What is a better way of doing this. I'am assigning either of two property values (from two different objects), depending on their existence, to a third data-structure.
In case the args object's value is nullish a non nullish value gets accessed from the default object and assigned to the final structure.
return {
first: {
visible: args.first?.visible ?? defaulttest.first?.visible,
emoji: args.first?.emoji ?? defaulttest.first?.emoji,
style: args.first?.style ?? defaulttest.first?.style,
},
back: {
visible: args.back?.visible ?? defaulttest.back?.visible,
emoji: args.back?.emoji ?? defaulttest.back?.emoji,
style: args.back?.style ?? defaulttest.back?.style,
},
page: {
visible: args.page?.visible ?? defaulttest.page?.visible,
emoji: args.page?.emoji ?? defaulttest.page?.emoji,
style: args.page?.style ?? defaulttest.page?.style,
},
forward: {
visible: args.forward?.visible ?? defaulttest.forward?.visible,
emoji: args.forward?.emoji ?? defaulttest.forward?.emoji,
style: args.forward?.style ?? defaulttest.forward?.style,
},
last: {
visible: args.last?.visible ?? defaulttest.last?.visible,
emoji: args.last?.emoji ?? defaulttest.last?.emoji,
style: args.last?.style ?? defaulttest.last?.style,
},
Mdelete: {
visible: args.Mdelete?.visible ?? defaulttest.Mdelete?.visible,
emoji: args.Mdelete?.emoji ?? defaulttest.Mdelete?.emoji,
style: args.Mdelete?.style ?? defaulttest.Mdelete?.style,
},
removeBtn: {
visible: args.removeBtn?.visible ?? defaulttest.removeBtn?.visible,
emoji: args.removeBtn?.emoji ?? defaulttest.removeBtn?.emoji,
style: args.removeBtn?.style ?? defaulttest.removeBtn?.style,
},
};

From my above comments ...
1/2 ... The OP actually is not really comparing. For a certain set of properties the OP looks up each property at a target object, and only in case it features a nullish value there will be an assignment from a source object's counterpart to the missing property. Thus an approach I would choose was ...
2/2 ... implementing a generic function which merges two objects in a way that a source property can only be written/assigned in case the target structure does not already provide a non nullish value. This function then has to be invoked twice once for args and defaulttest and a second time for the to be returned entirely empty data structure and args.
The above statement was a bit ambitious for there are at least 2 strategies of how one could achieve such kind of mergers.
Thus the below provided example code implements two approaches
one, called refit, which follows a pushing/patching agenda due to forcing the assignement of every non nullish property in a source-object to its non nullish counterpart of a target-object.
a 2nd one, called revive, which resembles a pulling approach for it just reassigns the nullish target-object properties with their non nullish source-object counterparts.
The difference in the results they produce for one and the same preset is going to be demonstrated herby ...
// "refit" ... a pushing/patching approach.
// - force the assignement of every non nullish property in source
// to its non nullish counterpart in target ... hence a *refit*.
function refitNullishValuesRecursively(target, source) {
if (
// are both values array-types?
Array.isArray(source) &&
Array.isArray(target)
) {
source
// for patching always iterate the source items ...
.forEach((sourceItem, idx) => {
// ... and look whether a target counterpart exists.
if (target[idx] == null) {
// either assign an existing structured clone ...
if (sourceItem != null) {
target[idx] = cloneDataStructure(sourceItem);
}
} else {
// ... or proceed recursively.
refitNullishValuesRecursively(target[idx], sourceItem);
}
});
} else if (
// are both values object-types?
source && target &&
'object' === typeof source &&
'object' === typeof target
) {
Object
// for patching ...
.entries(source)
// ... always iterate the source entries (key value pairs) ...
.forEach(([key, sourceValue], idx) => {
// ... and look whether a target counterpart exists.
if (target[key] == null) {
// either assign an existing structured clone ...
if (sourceValue != null) {
target[key] = cloneDataStructure(sourceValue);
}
} else {
// ... or proceed recursively.
refitNullishValuesRecursively(target[key], sourceValue);
}
});
}
return target;
}
// "revive" ... a pulling approach.
// - just reassign the nullish target properties with their
// non nullish source counterparts ... hence a *revive*.
function reviveNullishValuesRecursively(target, source) {
if (
// are both values array-types?
Array.isArray(target) &&
Array.isArray(source)
) {
target
// for fixing always iterate the target items.
.forEach((targetItem, idx) => {
if (targetItem == null) {
// either assign an existing structured clone ...
target[idx] = cloneDataStructure(source[idx]) ?? targetItem;
} else {
// ... or proceed recursively.
reviveNullishValuesRecursively(targetItem, source[idx]);
}
});
} else if (
// are both values object-types?
target && source &&
'object' === typeof target &&
'object' === typeof source
) {
Object
// for fixing ...
.entries(target)
// ... always iterate the target entries (key value pairs).
.forEach(([key, targetValue], idx) => {
if (targetValue == null) {
// either assign an existing structured clone ...
target[key] = cloneDataStructure(source[key]) ?? targetValue;
} else {
// ... or proceed recursively.
reviveNullishValuesRecursively(targetValue, source[key]);
}
});
}
return target;
}
const cloneDataStructure =
('function' === typeof structuredClone)
&& structuredClone
|| (value => JSON.parse(JSON.stringify(value)));
const targetBlueprint = {
x: { xFoo: 'foo', xBar: 'bar', xBaz: { xBiz: null } },
y: { yFoo: 'foo', yBar: null },
};
const patch = {
x: { xFoo: null, xBar: null, xBaz: { xBiz: 'biz' } },
y: { yFoo: null, yBar: 'bar', yBaz: { yBiz: 'biz' } },
};
let target = cloneDataStructure(targetBlueprint);
console.log('"refit" ... a pushing/patching approach.');
console.log('before refit ...', { target, patch });
refitNullishValuesRecursively(target, patch);
console.log('after refit ...', { target, patch });
target = cloneDataStructure(targetBlueprint);
console.log('"revive" ... a pulling approach.');
console.log('before revive ...', { target, patch });
reviveNullishValuesRecursively(target, patch);
console.log('after revive ...', { target, patch });
.as-console-wrapper { min-height: 100%!important; top: 0; }
As for the OP's example which targets the creation of kind of a config-object, one could fully patch/refit a clone of the temporary or current args-config, whereas within the last step one has control over the config-object's final structure by providing the most basic empty config-base which just gets revived by the before created full patch/refit-config.
function refitNullishValuesRecursively(target, source) {
if (Array.isArray(source) && Array.isArray(target)) {
source
.forEach((sourceItem, idx) => {
if (target[idx] == null) {
if (sourceItem != null) {
target[idx] = cloneDataStructure(sourceItem);
}
} else {
refitNullishValuesRecursively(target[idx], sourceItem);
}
});
} else if (
source && target &&
'object' === typeof source &&
'object' === typeof target
) {
Object
.entries(source)
.forEach(([key, sourceValue], idx) => {
if (target[key] == null) {
if (sourceValue != null) {
target[key] = cloneDataStructure(sourceValue);
}
} else {
refitNullishValuesRecursively(target[key], sourceValue);
}
});
}
return target;
}
function reviveNullishValuesRecursively(target, source) {
if (Array.isArray(target) && Array.isArray(source)) {
target
.forEach((targetItem, idx) => {
if (targetItem == null) {
target[idx] = cloneDataStructure(source[idx]) ?? targetItem;
} else {
reviveNullishValuesRecursively(targetItem, source[idx]);
}
});
} else if (
target && source &&
'object' === typeof target &&
'object' === typeof source
) {
Object
.entries(target)
.forEach(([key, targetValue], idx) => {
if (targetValue == null) {
target[key] = cloneDataStructure(source[key]) ?? targetValue;
} else {
reviveNullishValuesRecursively(targetValue, source[key]);
}
});
}
return target;
}
const cloneDataStructure =
('function' === typeof structuredClone)
&& structuredClone
|| (value => JSON.parse(JSON.stringify(value)));
const defaultConfig = {
first: {
visible: 'default.first.visible',
emoji: 'default.first.emoji',
style: 'default.first.style',
},
forward: {
visible: 'default.forward.visible',
emoji: 'default.forward.emoji',
style: 'default.forward.style',
},
removeBtn: {
visible: 'default.removeBtn.visible',
emoji: 'default.removeBtn.emoji',
style: 'default.removeBtn.style',
},
};
const currentConfig = {
first: {
visible: 'current.first.visible',
emoji: 'current.first.emoji',
style: 'current.first.style',
},
forward: {
visible: 'current.forward.visible',
emoji: null,
},
FOO: {
visible: 'current.FOO.visible',
emoji: 'current.FOO.emoji',
style: 'current.FOO.style',
}
};
function getConfiguration(baseConfig) {
return reviveNullishValuesRecursively(
cloneDataStructure(baseConfig),
refitNullishValuesRecursively(
cloneDataStructure(currentConfig),
defaultConfig,
),
);
}
console.log(
getConfiguration({
first: null,
forward: null,
removeBtn: null,
})
);
.as-console-wrapper { min-height: 100%!important; top: 0; }

If the structure of your object is the one you presented you can do:
function normalize(input, defaultValue) {
// Loop on the outer keys
Object.keys(input).forEach(mainKey => {
// Loop on the inner keys
Object.keys(input[mainKey]).forEach(key => {
// set the value of the key as itself or default if null
input[mainKey][key] = input[mainKey]?.[key] ?? defaultValue[mainKey]?.[key]
})
})
return input;
}
Calling normalize(args, defaulttest) you will loop on each inner key, check if it exist and if it does not exist you substitute it with the default in the same path.
Example:
const x = {
a: {a1: '1', a2: '2'},
b: {b1: '1', b2: null}
}
const y = {b: {b2: '5'}}
console.log(normalize(x,y))
Output:
{
"a": {
"a1": "1",
"a2": "2"
},
"b": {
"b1": "1",
"b2": "5"
}
}
With this approach you must have the key in the args input. If the key is missing, it will not be substituted with the default. To make it work even with not-present keys you need to use a third structure with all the possible path for example.

finding undefined or null value from object inside object

i would like to push keys inside array if found undefined or null
const obj = {
name:'ab',
edu:'av',
degres:{
a1:'',
b1:'1'
},
platform:undefined
}
i want an output like
`['a1','platform']`
as the value for a1 and platform were null and undefined
i have treid this solution but it doesnt work
function iterater(obj){
let blankValues = [];
Object.keys(obj).map((key) => {
if (obj.hasOwnProperty(key) && (typeof obj[key] === "object")) {
iterater(obj[key])
} else {
if (typeof obj[key] === "undefined" || obj[key] === ''){
blankValues.push(key);
}
}
})
return blankValues;
}
but this somehow only return ['platform'] only,but the expected output should be ['platform','a1'],i think when running iterater(obj[key]),the value of array (blankValues) gets blank as it doesnt perserve it,but please help me with appropriate logic and structure

The issue is because you're re-defining blankValues as an empty array in every iteration of the recursive loop. To fix this you could accept the array as an optional argument of the function so that values get pushed to it on each iteration.
Also note that, as #ziggy wiggy pointed out in the comments, your logic will fail when a null value is encountered as typeof obj[key] === "object" would be true. You need a specific null check too.
const obj = {
name: 'ab',
edu: 'av',
degres: {
a1: '',
b1: '1'
},
platform: undefined,
foo: null
}
function iterater(obj, arr) {
arr = arr || [];
Object.keys(obj).map((key) => {
if (obj.hasOwnProperty(key) && (typeof obj[key] === "object") && obj[key] !== null) {
iterater(obj[key], arr)
} else {
if (typeof obj[key] === "undefined" || obj[key] === null || obj[key].trim() === '') {
arr.push(key);
}
}
})
return arr;
}
console.log(iterater(obj));
Note that I also added a trim() call to test the empty string. Your previous logic would accept whitespace-filled strings as valid values.

As you said yourself, when you call iterater(obj[key]) it sets a new local blankValues and puts values in it. So i think you should put blankValues outside the function.
And then you don't have to return it (or you can if you want it as a return value).
Or you can pass blankValues as a parameter of iterater in both the main call and the "inside" call

You need to consume the result of recursive call. For example add it back to blankValues like this blankValues.push(...iterater(obj[key]))
const obj = {
name:'ab',
edu:'av',
degres:{
a1:'',
b1:'1'
},
platform:undefined
}
function iterater(obj){
let blankValues = [];
Object.keys(obj).map((key) => {
if (obj.hasOwnProperty(key) && (typeof obj[key] === "object")) {
blankValues.push(...iterater(obj[key]))
} else {
if (typeof obj[key] === "undefined" || obj[key] === ''){
blankValues.push(key);
}
}
})
return blankValues;
}
console.log(iterater(obj))

You must push the result returned by the recursive call to your array.
Change:
iterater(obj[key])
for:
blankValues.push(...iterater(obj[key]))
const obj = {
name: 'ab',
edu: 'av',
degres: {
a1: '',
b1: '1'
},
platform: undefined
}
function iterater(obj){
let blankValues = [];
Object.keys(obj).map((key) => {
if (obj.hasOwnProperty(key) && (typeof obj[key] === "object")) {
blankValues.push(...iterater(obj[key]))
} else {
if (typeof obj[key] === "undefined" || obj[key] === ''){
blankValues.push(key);
}
}
})
return blankValues;
}
console.log(iterater(obj));
Here is another way to do it using Object.entries(), Object.keys(), Array.reduce(), Array.flat() and Array.isArray(). This implementation works for arrays too.
const obj = {
name:'ab',
edu:'av',
something: [{ a: 1 }, { a: '' }],
degres:{
a1:'',
b1:'1'
},
platform:undefined
};
function getEmptyProps(obj) {
if (!Object.keys(obj).length) { return []; }
return Object.entries(obj).reduce((acc, [key, val]) => {
if (val === undefined || val === null || val.toString().trim() === '') {
acc.push(key);
} else if (Array.isArray(val)) {
acc.push(val.map(getEmptyProps).flat());
} else if (typeof val === 'object') {
acc.push(getEmptyProps(val));
}
return acc.flat();
}, []);
}
console.log(getEmptyProps(obj))

You could take a check for falsy keys and return the key, if the property is an object, the check the object.
const
getFalsy = o => Object.keys(o).reduce((r, k) => {
if (!o[k]) return [...r, k];
if (typeof o[k] === 'object') return [...r, ...getFalsy(o[k])];
return r;
}, []),
object = { name: 'ab', edu: 'av', degres: { a1: '', b1: '1' }, platform: undefined };
console.log(getFalsy(object));

ES6 Spread operator to vanilla Javascript

I have added a script that uses ES6 spread operator to the project that gets the params from the url. Unsure how to revert this to the normal vanilla Javascript syntax after I discovered that the project doesn't support ES6.
It's easy to take normal Javascript arrays and use the spread operator but in more complicated instances like this one I cannot make the array return the result without totally changing the script.
getQueryURLParams("country");
getQueryURLParams = function(pName) {
var urlObject = location.search
.slice(1)
.split('&')
.map(p => p.split('='))
.reduce((obj, pair) => {
const [key, value] = pair.map(decodeURIComponent);
return ({ ...obj, [key]: value }) //This is the section that needs to be Vanilla Javascript
}, {});
return urlObject[pName];
};
Thanks to everyone for the replies. After back and forth I realized that the suggestion here that I convert the whole script to ES5 was correct since the browser only complained about that line but other items not ES5 were also problematic.
This is what I had after using ES5:
getQueryURLParams = function(pName) {
if (typeof Object.assign != 'function') {
// Must be writable: true, enumerable: false, configurable: true
Object.defineProperty(Object, "assign", {
value: function assign(target, varArgs) { // .length of function is 2
'use strict';
if (target == null) { // TypeError if undefined or null
throw new TypeError('Cannot convert undefined or null to object');
}
var to = Object(target);
for (var index = 1; index < arguments.length; index++) {
var nextSource = arguments[index];
if (nextSource != null) { // Skip over if undefined or null
for (var nextKey in nextSource) {
// Avoid bugs when hasOwnProperty is shadowed
if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
to[nextKey] = nextSource[nextKey];
}
}
}
}
return to;
},
writable: true,
configurable: true
});
}
var urlObject = location.search
.slice(1)
.split('&')
.map(function(element ) {
return element.split('=');
})
.reduce(function(obj, pair) {
const key = pair.map(decodeURIComponent)[0];
const value = pair.map(decodeURIComponent)[1];
return Object.assign({}, obj, { [key]: value });
}, {});
return urlObject[pName];
};

You can use Object.assign():
return Object.assign({}, obj, { [key]: value });
Demo:
const obj = { a: 1 };
const key = 'b';
const value = 2;
console.log(Object.assign({}, obj, { [key]: value }));
FWIW, the { ...obj } syntax is called "Object Rest/Spread Properties" and it's a part of ECMAScript 2018, not ECMAScript 6.

Since you want the syntax for ES5 here is a polyfill for Object.assing() (source: MDN)
// we first set the Object.assign function to null to show that the polyfill works
Object.assign = null;
// start polyfill
if (typeof Object.assign != 'function') {
// Must be writable: true, enumerable: false, configurable: true
Object.defineProperty(Object, "assign", {
value: function assign(target, varArgs) { // .length of function is 2
'use strict';
if (target == null) { // TypeError if undefined or null
throw new TypeError('Cannot convert undefined or null to object');
}
var to = Object(target);
for (var index = 1; index < arguments.length; index++) {
var nextSource = arguments[index];
if (nextSource != null) { // Skip over if undefined or null
for (var nextKey in nextSource) {
// Avoid bugs when hasOwnProperty is shadowed
if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
to[nextKey] = nextSource[nextKey];
}
}
}
}
return to;
},
writable: true,
configurable: true
});
}
// end polyfill
// example, to test the polyfill:
const object1 = {
a: 1,
b: 2,
c: 3
};
const object2 = Object.assign({c: 4, d: 5}, object1);
console.log(object2.c, object2.d);
// expected output: 3 5

Remove number properties from an object?

I'm trying to remove properties that are numbers from an object:
function removeNumberValues(obj) {
for (i in obj) {
if (obj['i'] instanceof Number) {
delete obj['i'];
}
}
return obj;
}
But it's not removing numerical properties. Halp? What am I missing?

You need to use the variable i, not the value 'i', and you could check with typeof operator and number as value.
function removeNumberValues(object) {
var key;
for (key in object) {
if (typeof object[key] === 'number') {
delete object[key];
}
}
return object;
}
console.log(removeNumberValues({ a: 'foo', b: 42 }));
With Object.keys and Array#forEach for iterating the keys.
function removeNumberValues(object) {
Object.keys(object).forEach(function (key) {
if (typeof object[key] === 'number') {
delete object[key];
}
});
return object;
}
console.log(removeNumberValues({ a: 'foo', b: 42 }));

Use typeof instead. It's more reliable in this case. Unless the value derives from a Number constructor it's not gonna work.
const obj = {
str: "string",
num: 1,
str2: "string2",
num2: 2
};
console.log(removeNumberValues(obj));
function removeNumberValues(obj) {
Object.keys(obj).forEach(function(key) {
if (typeof obj[key] === 'number') {
delete obj[key];
}
});
return obj;
}

Access to object property with dynamic name and dynamic nesting level

I read the property of an object I want to access from a string: level1.level2.property OR level1.property OR ... The names and the nesting may vary. I store the objects in a separate module (workerFunctions).
I know that I can access the objects dynamically with the []notation, e.g.:
var level1="level1";
var property="property";
console.log(workerFunctions[level1][property])
However, I don't know how to construct this "workerFunctions[level1][property]" dynamically from varying input strings, so to produce e.g.:
console.log(workerFunctions[level1][level2][property])
in consequence of the string: level1.level2.property.
Thank you in advance.

You could split the path and use the parts as properties for the given object.
function getValue(o, path) {
return path.split('.').reduce(function (o, k) {
return (o || {})[k];
}, o);
}
var o = { A : { B: { C: { value: 'Brenda' } } } };
console.log(getValue(o, 'A.B.C').value); // Brenda
console.log(getValue(o, 'Z.Y.X')); // undefined
For better use with dots in properties, you could use an array directly to avoid wrong splitting.
function getValue(o, path) {
return path.reduce(function (o, k) {
return (o || {})[k];
}, o);
}
var o = { A : { 'B.C': { value: 'Brenda' } } };
console.log(getValue(o, ['A', 'B.C', 'value'])); // Brenda
console.log(getValue(o, ['Z.Y.X'])); // undefined

This should do it :
const str = 'level1.level2.property';
let value = { //workerFunctions;
level1: {
level2: {
property: 'this is the value'
}
}
};
str.split(/\./).forEach((prop) => {
value = value[prop];
});
console.log(value);