Can't implement simple optional chaining - javascript

I am trying to implement a simple optional chaining state update. What I want is for the items to ONLY be changed IF the item is defined/exists; if not/is undefined, I want the item to keep the previous state (e.g userID should remain = 2 if not updated).
To test this out I created an object with three variables:
const userObj = {
firstName: "",
lastName: "",
userID: 2,
};
Then I created a function to update state:
const updateState = (item) => {
return {
userObj.firstName = item?.firstName,
userObj.lastName = item?.lastName,
userObj.userID = item?.userID,
};
};
Finally I pass the item which contains only one item to update (firstName) and I call the function:
const item = {
firstName: "None",
};
console.log(updateState(item));
The output:
userObj.firstName = item?.firstName,
^
SyntaxError: Unexpected token '.'
But when I hover over userObj I can see its properties:

You get this error because what you are trying to return is an object with dots in its keys.
You're mixing assignment and object creation. In addition item?.firstName only helps with the case that item is null or undefined in a sense that it fails fast instead of throwing an exception because you can't access null.firstName.
For this kind of default you'd have to do something along the lines of typeof item.firstName === 'string' ? item.firstName : userObj.firstName.
To pull everything together:
const func = (value, fallback) => (
typeof value === typeof fallback
? value
: fallback
);
const updateState = (item) => {
userObj.firstName = func(item?.firstName, item.firstName);
userObj.lastName = func(item?.lastName, item.lastName);
userObj.userID = func(item?.userID, item.userId);
return userObj;
};
Note however that this function will mutate userObj.
Edit: default was a poor naming choice.

You can do it this way, using javascript object destructuring
const updateState = (item) => {
return {
...userObj,
...item,
};
};
so it will only update the key and value that was passed, i hope the question is not on typescript

You can use null coalescing in conjunction with optional chaining:
const updateState = item => ({
userObj.firstName = item?.firstName ?? userObj.firstName ,
userObj.lastName = item?.lastName ?? userObj.lastName ,
userObj.userID = item?.userID ?? userObj.userId ,
});
You could use the spread operator:
const updateState = item => {
userObj = { ...userObj, ...item };
return userObj;
}
Or you can use lodash's defaults() function:
const _ = require('lodash');
const updateState = item => {
userObj = _.defaults(userObj, item)
return userObj;
}
Or... if you really want to mutate the state object, rather than creating a new one and replacing it, roll your own, similar:
const updateState = item => {
for (const key in item ) {
const hasValue = key != null && key != undefined && key != NaN ;
if ( hasValue ) {
userObj[prop] = item[prop];
}
}
}
There is, as they say, more than one way to skin a cat.
[Edited: Add explanation of the spread operator]
The spread operator,
const obj = { ...obj1, ...obj2, . . . , ...objN };
is somewhat akin to calling a function like this:
const obj = mergeObjects( obj1, obj2, . . ., objN );
where mergeObjects() is defined as:
function mergeObjects(...objects) {
const mergedObject = {};
for (const obj of objects ) {
for (const key in obj ) {
mergedObject[key] = item[key];
}
}
return mergedObject;
}
Or perhaps a better explanation might be done using Object.assign(). One could say that an expression like:
const obj = {
prop1: 'a' ,
prop2: 'b' ,
...obj1 ,
prop3: 'c' ,
prop4: 'd' ,
...obj2 ,
prop5: 'e' ,
prop6: 'f' ,
...obj3 ,
}
is the equivalent of this:
const obj = Object.assign( {},
{
prop1: 'a' ,
prop2: 'b' ,
},
obj1 ,
{
prop3: 'c' ,
prop4: 'd' ,
} ,
obj2 ,
{
prop5: 'e' ,
prop6: 'f' ,
} ,
obj3 ,
);

Related

Conditionally assign from part of an object

I think there's an elegant way to do this (maybe using destructuring), but I'm stumped so far. I'd like to assign some of the keys and values from one object to another, conditionally based on a boolean.
function bigObject() {
return { /* an object with lots of keys and values, lots */ }
}
function myFunction(aBool) {
// I want smallObject to be either empty or contain a subset of bigObject, based on aBool
// here's where I am stuck
let smallObject = aBool ? { keyA, keyB } = bigObject() : {};
}
JS complains that keyA is a reference error, and I can see how, even if I had this right, I'd just end up creating keyA and keyB variables, not smallObject as I want.
I know I can do this:
let smallObject = {};
if (aBool) {
let bigObject = bigObject();
smallObject.keyA = bigObject.keyA;
smallObject.keyB = bigObject.keyB;
smallObject.keyC = bigObject.keyC;
// 5 of these
}
But that sure is a lot of stuff to write when I think there's a way I can write just the props names.
It's not a problem to use temporary destructuring variables. Just use them again to build the target object. If you want it in one expression, you can use an inline function that performs the destructuring in its parameter variables, and then returns the new object:
let smallObject = aBool ? (
({ keyA, keyB }) => ({ keyA, keyB })
) (bigObject()) : {};
const bigObject = () => ({ keyA: 1, keyB: 2, keyC: 3, keyD: 4});
let aBool = true;
let smallObject = aBool ? (
({ keyA, keyB }) => ({ keyA, keyB })
) (bigObject()) : {};
console.log(smallObject);
You could use an IIFE that returns a destructured object.
const bigObject = {
keyA: 'a',
keyB: 'b',
keyC: 'c',
};
const getObj = (aBool) =>
aBool
? (({ keyA, keyB }) => ({ keyA, keyB }))(bigObject)
: {};
console.log(getObj(true));
Or you could write your own "plucking" function to return a new object based on the original:
const bigObject = {
keyA: 'a',
keyB: 'b',
keyC: 'c',
};
const pluck = (obj, callback) => callback(obj);
const getObj = (aBool) =>
aBool
? pluck(bigObject, ({ keyA, keyB }) => ({ keyA, keyB }))
: {};
console.log(getObj(true));
Option 1
if (aBool) smallObject = { ...smallObject, ...bigObject};
Option 2
if (aBool) {
Object.entries(bigObject).forEach(([key, value]) => smallObject[key] = value);
}

Filter nested object

I receive an object that looks like this:
this.tokensData = {
O: {
id: 0,
name: value1,
organization: organization1,
...,
},
1: {
id: 1,
name: value1,
organization: organization1,
...,
},
2: {
id: 2,
name: value2,
organization: organization2,
...,
},
...
}
I want to filter by id and remove the Object which id matches the id I receive from the store. What I tried so far:
const filteredObject = Object.keys(this.tokensData).map((token) => {
if (this.$store.state.id !== this.tokensData[token].id) {
return this.tokensData[token];
}
});
This replaces the Object with undefined - which would work for my purposes but is obviously not ideal.
Any help is much appreciated!
Try to use Object.entries and then Object.fromEntries() to create an object from a list of key-value pairs:
let store = [0 , 1];
const result = Object.entries(tokensData).filter(([k, v]) => !store.some(s => s == v.id));
console.log(Object.fromEntries(result));
An example:
let tokensData = {
O: {
id: 0,
name: '',
organization: '',
},
1: {
id: 1,
name: '',
organization: '',
},
2: {
id: 2,
name: '',
organization: '',
}
}
let store = [0 , 1];
const result = Object.entries(tokensData).filter(([k, v]) => !store.some(s => s == v.id));
console.log(Object.fromEntries(result));
You can do this by using Object.entries and Object.fromEntries:
const filteredObject = Object.fromEntries(
Object.entries(this.tokensData).filter(
([key, value]) => value.id !== this.$store.state.id
)
)
This can be done by cloning the object and removing the object at the ID:
const removeObjectByID = (obj, id) => {
// first create a copy of the object
const copy = JSON.parse(JSON.stringify(obj))
// next, delete the one entry you don't want
delete copy[id]
// finally, return the new object
return copy
}
// Test
const data = {a:1, b: 2, c: 3}
console.log(removeObjectByID(data, 'b')) // { a: 1, c: 3 }
The problem with undefined is caused by using this in your arrow function. Javascript scoping gives a different meaning to this if the function is a arrow function.
Furthermore I suggest to use filter.
.map is used to transform A -> B.
.filter should be used to filter out objects.
Now if we combine that this would become something like this.
function filterById(token) {
return this.$store.state.id !== this.tokensData[token].id;
}
function getTokenData(token) {
return this.tokensData[token]
}
const token = Object.keys(this.tokensData)
.filter(filterById)
.map(getTokenData);
});
Please note that I'm not using arrow functions. Arrow function can't refer to this due to the way javascript handles scoping.
An alternative approach could be to reference this into a variable, so your arrow function can access the variable.
const self = this;
const token = Object.keys(this.tokensData)
.filter(token => self.$store.state.id !== self.tokensData[token].id)
.map(token => self.tokensData[token]);
Too make it even nicer you could utilize Object.entries. This will return an array of key and value, which you can destructure using es6 syntax as following [key, value].
const self = this;
const token = Object.entries(this.tokensData)
.filter(([key, value]) => self.$store.state.id !== value.id)
.map(([key, value]) => value);

Iterate object keys to replace the selected one with desired keys using es6 array functions

I have a requirement to replace the available keys with the desired keys in an object for which I was trying to execute below code, which later I found out to be incorrect usage of filter for desired output. hence I need help in getting the desired results using es6 array functions.
const columns = Object.keys(someArray).filter((columnName) => {
if (someCheck === "somecheck") {
if (columnName === 'MyName') {
const newcolumnName = `Pranav`;
return newcolumnName;
} else if (columnName === 'YourName') {
const newcolumnName = `Alex`;
return newcolumnName;
}
} else {
return (columnName !== 'sometingelse') ? columnName : '';
}
}
);
Here the someArray is as below:
someArray{
abc:"djfhdjf",
xyz:"ssss",
MyName:"onename",
YourName:"somename",
sometingelse:'somevalue'
}
I am expecting columns to be:
columns{
abc:"djfhdjf",
xyz:"ssss",
Pranav:"onename",
Alex:"somename",
sometingelse:'somevalue'
}
Please suggest how can I achieve the above expected output?
Note: I dont want to use function keyword in callbacks to avoid eslint errors
You could filter the wanted keys for replacement and replace the keys by using a new key and eleting the old one.
const
object = { abc: "djfhdjf", xyz: "ssss", MyName: "onename", YourName: "somename", sometingelse: 'somevalue' },
replacements = { MyName: 'Pranav', YourName: 'Alex', sometingelse: '' };
Object
.keys(object)
.filter(k => k in replacements)
.forEach(k => {
object[replacements[k]] = object[k];
delete object[k];
});
console.log(object);
For generating an object, you could map new objects and assign them to a single object.
const
object = { abc: "djfhdjf", xyz: "ssss", MyName: "onename", YourName: "somename", sometingelse: 'somevalue' },
replacements = { MyName: 'Pranav', YourName: 'Alex', sometingelse: '' },
result = Object.assign(...Object
.entries(object)
.map(([k, v]) => ({ [k in replacements ? replacements[k] : k]: v }))
);
console.log(result);
const obj = {
abc: 'djfhdjf',
xyz: 'ssss',
MyName: 'onename',
YourName: 'somename',
sometingelse: 'somevalue'
};
const newObj = Object.keys(obj).reduce((acc, key) => {
if (key === 'MyName') {
acc.newMyName = obj[key];
} else if (key === 'YourName') {
acc.newYourName = obj[key];
} else {
acc[key] = obj[key];
}
return acc;
}, {});
console.log('newObj = ', newObj);
Here is my approach, a bit long solution, but its on purpose so you can see how to do it simple without too much abstraction:
const someArray = {
abc:"djfhdjf",
xyz:"ssss",
MyName:"onename",
YourName:"somename",
sometingelse:'somevalue'
}
let foo = Object.keys(someArray).map(key => {
if(key === 'MyName') {
return 'Alex'
} else if(key === 'YourName') {
key = 'Pranav'
}
return key;
})
let bar = Object.entries(someArray).map((el, i) => {
el[0] = res[i];
return el;
})
let baz = r.reduce((acc, el)=>{
acc[`${el[0]}`] = el[1];
return acc;
},{})
console.log(baz);
You could use .reduce like so. It uses a similar idea that Nina proposed by using an object to hold your replacements. Here I have used the spread syntax to add the changed key to the accumulated object, along with it's associated value.
const someArray = {abc: "djfhdjf", xyz: "ssss", MyName: "onename", YourName: "somename", sometingelse: 'somevalue'},
toUse = {MyName: "Pranav", YourName: "Alex"}, // define the keys you want to change and what they should change to
res = Object.keys(someArray).reduce((acc, key) =>
({...acc, [key in toUse ? toUse[key] : key]:someArray[key]})
, {});
console.log(res);
I am running a reduce on the keys of some array starting with an empty object. The ...acc spreads out all the properties in the reduced object. ...{ [keysMap[key] || key]: obj[key] } checks if the current key is present in keysMap.If it is present,it uses that key (keysMap[key]) otherwise it just uses the keys of the existing object.(|| key).Hope that makes sense
const renameKeys = (keysMap, obj) =>
Object.keys(obj).reduce(
(acc, key) => ({
...acc,
...{ [keysMap[key] || key]: obj[key] }
}),
{}
)
const columns = renameKeys({'MyName':'Pranav','YourName':'Alex'},someArray)

How to convert snake case to camelcase in my app

I have a very weird issue in my lodash codes
I have something like
data = {
'id':'123',
'employee_name': 'John',
'employee_type': 'new'
}
var newObj = _.mapValues(data, function (value, key) {
var t = _.camelCase(key);
console.log(t) -> shows employeeName and employeeType
return _.camelCase(key);
});
I was expecting my newObj will become
data = {
'id':'123',
'employeeName': 'John',
'employeeType': 'new'
}
after I ran the codes above, it still stays the same as it was like
data = {
'id':'123',
'employee_name': 'John',
'employee_type': 'new'
}
This is super weird and I'm not sure what went wrong. Can someone help me about this? Thanks a lot!
replacing snake_case or kebab-case to camelCase only for string (ES6+):
const snakeToCamel = str =>
str.toLowerCase().replace(/([-_][a-z])/g, group =>
group
.toUpperCase()
.replace('-', '')
.replace('_', '')
);
result:
console.log(snakeToCamel('TO_CAMEL')) //toCamel
console.log(snakeToCamel('to_camel')) //toCamel
console.log(snakeToCamel('TO-CAMEL')) //toCamel
console.log(snakeToCamel('to-camel')) //toCamel
Use _.mapKeys() instead of _.mapValues():
var data = {
'id': '123',
'employee_name': 'John',
'employee_type': 'new'
};
var newObj = _.mapKeys(data, (value, key) => _.camelCase(key));
console.log('newObj: ', newObj);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.2/lodash.min.js"></script>
If you need to ignore the redundant value param, you can use _.rearg() on _.camelCase() to generate a function that takes the 2nd param (the key) instead of the 1st param (the value).
var data = {
'id': '123',
'employee_name': 'John',
'employee_type': 'new'
};
var newObj = _.mapKeys(data, _.rearg(_.camelCase, 1));
console.log('newObj: ', newObj);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.2/lodash.min.js"></script>
You can also easily create your own function for that:
function camelCase(obj) {
var newObj = {};
for (d in obj) {
if (obj.hasOwnProperty(d)) {
newObj[d.replace(/(\_\w)/g, function(k) {
return k[1].toUpperCase();
})] = obj[d];
}
}
return newObj;
}
var data = {
'id': '123',
'employee_name': 'John',
'employee_type': 'new'
}
console.log(camelCase(data));
Here's how to do it in native Javascript...
let data = {
'id':'123',
'employee_name': 'John',
'employee_type': 'new'
}
// #1 simple function which converts a string from snake case to camel case ...
const snakeToCamel = s => s.replace(/(_\w)/g, k => k[1].toUpperCase())
// #2 create new data object with camelCase keys...
data = Object.entries(data).reduce((x,[k,v]) => (x[snakeToCamel(k)]=v) && x, {})
console.log(data)
For my use case I needed (or wanted) a function that would handle any arbitrary json object, including nested objects, arrays, etc. Came up with this, seems to be working so far:
const fromSnakeToCamel = (data) => {
if (_.isArray(data)) {
return _.map(data, fromSnakeToCamel);
}
if (_.isObject(data)) {
return _(data)
.mapKeys((v, k) => _.camelCase(k))
.mapValues((v, k) => fromSnakeToCamel(v))
.value();
}
return data;
}
Note that if it's not an array or an object, I just return the data because I only actually want to convert keys. Anyway, hope this helps someone
These are all good answers, but they did not fit what I needed. I like Ashish's answer because it handles nested objects, but what if there are underscores in the data that you want? So, here is a varient on Bambam's answer to make it recursive, because lodash can sometimes be a pain.
function toCamelCase (obj) {
let rtn = obj
if(!rtn) {
return rtn
} else if (typeof (obj) === 'object') {
if (obj instanceof Array) {
rtn = obj.map(toCamelCase)
} else {
rtn = {}
for (let key in obj) {
if (obj.hasOwnProperty(key)) {
const newKey = key.replace(/(_\w)/g, k => k[1].toUpperCase())
rtn[newKey] = toCamelCase(obj[key])
}
}
}
}
return rtn
}
TypeScript
As always, nobody asked for typescript version, but here it is, please don't beat me ^-^.
Without _, No RegExp
I split functions in two modules but you can keep them outside with proper naming
I put never to mark out that the type is actually correct since TS doesn't always know if it is.
You still can use _ and get code shorter but I wanted to breakdown the process.
module CaseTransform {
export type Snake = Lowercase<`${string}_${string}`>
export type Camel = Capitalize<string> | `${Capitalize<string>}${Capitalize<string>}`
export type SnakeToCamel<S extends string> = S extends `${infer Start}_${infer Rest}` ? `${Start}${Capitalize<SnakeToCamel<Rest>>}` : S
type SnakeToCamel__TEST__ = SnakeToCamel<"my_account_profile"> // myAccountProfile
export function capitalize<S extends string>(string: S): Capitalize<S> {
if (string.length === 0) return "" as never
return (string[0].toUpperCase() + string.slice(1)) as never
}
export function snakeToCamel<S extends string>(string: S): SnakeToCamel<S> {
const [start, ...rest] = string.split("_")
return (start + rest.map(capitalize)) as never
}
const snakeToCamel__TEST__ = snakeToCamel("ASD_asd_asdad_")
}
module ObjectTransform {
export function snakeToCamel<O extends object, K extends keyof O>(object: O): { [P in K as (P extends CaseTransform.Snake ? CaseTransform.SnakeToCamel<P> : P)]: O[P] } {
return Object
.entries(object)
.reduce((result, [key, value]) => ({
...result,
[CaseTransform.snakeToCamel(key)]: value
}), {}) as never
}
}
const sample = {
id: 123,
employee_name: "John",
employee_type: "new",
camelCase: "123",
PascalCase: "123"
}
const __TEST__ = ObjectTransform.snakeToCamel(sample)
Note
If you want all characters (even abbreviations) to be in lowercase, put .toLowercase() after string AND change SnakeToCamel type to
type SnakeToCamel<S extends string> = S extends `${infer Start}_${infer Rest}` ? `${Lowercase<Start>}${Capitalize<SnakeToCamel<Rest>>}` : Lowercase<S>
Easy!
Typings Result
JavaScript Playground
function capitalize(string) {
if (string.length === 0) return ""
return (string[0].toUpperCase() + string.slice(1))
}
function snakeToCamel(string){
const [start, ...rest] = string.split("_")
return (start + rest.map(capitalize).join(""))
}
const snakeToCamel__TEST__ = snakeToCamel("ASD_asd_asdad_")
console.log(snakeToCamel__TEST__)
function objectKeysSnakeToCamel(object) {
return Object
.entries(object)
.reduce((result, [key, value]) => ({
...result,
[snakeToCamel(key)]: value
}), {})
}
const sample = {
id: 123,
employee_name: "John",
employee_type: "new",
camelCase: "123",
PascalCase: "123"
}
const __TEST__ = objectKeysSnakeToCamel(sample)
console.log(__TEST__)
Here is another answer using simple for loop.
var data = {
'id': '123',
'employee_name': 'John',
'employee_type': 'new'
};
var output = {}
for (var key in data) {
output[_.camelCase(key)] = data[key];
}
Try this it will definitely work as expected.
const helpers = {};
helpers.camelize = function(str) {
return str.trim().replace(/[A-Z]+/g, (letter, index) => {
return index == 0 ? letter.toLowerCase() : '_' + letter.toLowerCase();
}).replace(/(.(\_|-|\s)+.)/g, function(subStr) {
return subStr[0]+(subStr[subStr.length-1].toUpperCase());
});
}
helpers.camelizeKeys = function(data) {
const result = {};
for (const [key, val] of Object.entries(data)) {
result[helpers.camelize(key)] = val;
}
return result;
}
helpers.camelizeNestedKeys = function(dataObj) {
return JSON.parse(JSON.stringify(dataObj).trim().replace(/("\w+":)/g, function(keys) {
return keys.replace(/[A-Z]+/g, (letter, index) => {
return index == 0 ? letter.toLowerCase() : '_' + letter.toLowerCase();
}).replace(/(.(\_|-|\s)+.)/g, function(subStr) {
return subStr[0]+(subStr[subStr.length-1].toUpperCase());
});
}));
}
const data = {
'id':'123',
'employee_name': 'John',
'employee_type': 'new'
};
const nestedData = {
'id':'123',
'employee_name': 'John',
'employee_type': 'new',
'exployee_projects': [
{"project_name": "test1", "project_year": 2004},
{"project_name": "test2", "project_year": 2004}
]
};
// Few camelize Examples
const str1 = "banana_orange_apple_mango";
const str2 = "banana-orange-apple-mango";
const str3 = "banana orange apple mango";
const str4 = "BANANA Orange APPLE-mango";
const str5 = "banana 5orange apple #mango";
const str6 = "banana__orange-_apple5-#mango";
console.log(helpers.camelize(str1));
console.log(helpers.camelize(str2));
console.log(helpers.camelize(str3));
console.log(helpers.camelize(str4));
console.log(helpers.camelize(str5));
console.log(helpers.camelize(str6));
console.log("=============================");
// camelize object keys
console.log(helpers.camelizeKeys(data));
console.log("=============================");
// camelize nested object keys
console.log(helpers.camelizeNestedKeys(nestedData));
If you want to convert the nested object, then using lodash can be a bit painful.
I tried using regex, JSON.parse & JSON.stringify
and here is the code for the same
below code returns the new object that is having camel case instead of snake case
//input
var data = {
'id': '123',
'employee_name': 'John',
'employee_type': {'new_name': 'foo'}
};
JSON.parse(JSON.stringify(data).replace(
/(_\w)\w+":/g,
match => match[1].toUpperCase() + match.substring(2)
));
{
'id': '123',
'employeeName': 'John',
'employeeType': {'newName': 'foo'}
}
Based on Abbos Tajimov's answer (and Ali's comment), we could also take advantage of the arguments passed down to the inline function.
const snakeToCamel = str => {
if (!(/[_-]/).test(str)) return str
return str.toLowerCase()
.replace(/([-_])([a-z])/g, (_match, _p1, p2) => p2.toUpperCase())
}
camelCase(str) {
return str
.toLowerCase()
.replace(/([-_][a-z])/g, (ltr) => ltr.toUpperCase())
.replace(/[^a-zA-Z]/g, '')
}
another way
_(data)
.keys()
.map(_.camelCase)
.zipObject(_.values(data))
.value()
I really like Mardok's version with nested objects, only issue is that it converts "null" to {}
here mine:
import _ from 'lodash';
export const toCamelCase: any = (obj: any) => {
let rtn = obj
if (typeof obj === 'object') {
if (obj instanceof Array) {
rtn = obj.map(toCamelCase)
}
else if (_.isEmpty(obj)) {
rtn = null
} else {
rtn = {}
for (let key in obj) {
if (obj.hasOwnProperty(key)) {
const newKey = key.replace(/(_\w)/g, k => k[1].toUpperCase())
rtn[newKey] = toCamelCase(obj[key])
}
}
}
}
return rtn
}
Creates camelized object recursively.
function camelCase(obj) {
const newObj = {};
for (const key in obj) {
if (obj.hasOwnProperty(key)) {
const value = obj[key];
const keyCamel = key.replace(/(\_\w)/g, (match) => match[1].toUpperCase());
const isRecursive = typeof value === 'object';
newObj[keyCamel] = isRecursive ? camelCase(value) : value;
}
}
return newObj;
}
let data = {
id: '123',
employee_name: 'John',
inner: {
employee_type: 'new'
},
}
camelCase(data);
Found in typeorm repo https://github.com/typeorm/typeorm/blob/master/src/util/StringUtils.ts#L8
export function camelCase(str: string, firstCapital: boolean = false): string {
return str.replace(
/^([A-Z])|[\s-_](\w)/g,
function (match, p1, p2, offset) {
if (firstCapital === true && offset === 0) return p1
if (p2) return p2.toUpperCase()
return p1.toLowerCase()
},
)
}
Use npm json-case-handler which will allow you to do this in one line.
It can convert any nested objects
For your case, you can do this :
const jcc = require('json-case-convertor')
const snakeCasedJson = jcc.snakeCaseKeys(yourjsonData)
Just pass the value to input and the result will be camelcase:
const snakeToCamel = input =>
console.log(
input.slice(0, input.indexOf('_')).toLowerCase() +
input[input.indexOf('_') + 1].toUpperCase() +
input.slice(input.indexOf('_') + 2)
);
const inputs = [
'underscore_case',
'first_name',
'Some_Variable',
'calculate_AGE',
'delayed_departure',
'Hello_you',
'hAI_i',
];
for (let input of inputs) {
snakeToCamel(input);
}
This function will recursively convert all snake case keys in the object to camelCase. Including objects within arrays and object within objects.
const convertSnakeCaseToCamelCase = (obj) => {
let newObj = {};
if (typeof(obj) !== 'object') {
return obj;
} else if (Array.isArray(obj)) {
newObj = [];
}
for (const key in obj) {
const childObj = convertSnakeCaseToCamelCase(obj[key]);
if (Array.isArray(obj)) {
newObj.push(childObj);
} else {
const newKey = key.replace(/(\_\w)/g, (k) => k[1].toUpperCase());
newObj[newKey] = childObj;
}
}
return newObj;
};

Remove a property in an object immutably

I am using Redux. In my reducer I'm trying to remove a property from an object like this:
const state = {
a: '1',
b: '2',
c: {
x: '42',
y: '43'
},
}
And I want to have something like this without having to mutate the original state:
const newState = {
a: '1',
b: '2',
c: {
x: '42',
},
}
I tried:
let newState = Object.assign({}, state);
delete newState.c.y
but for some reasons, it deletes the property from both states.
Could help me to do that?
How about using destructuring assignment syntax?
const original = {
foo: 'bar',
stack: 'overflow',
};
// If the name of the property to remove is constant
const { stack, ...withoutFirst } = original;
console.log(withoutFirst); // Will be { "foo": "bar" }
// If the name of the property to remove is from a variable
const key = 'stack'
const { [key]: value, ...withoutSecond } = original;
console.log(withoutSecond); // Will be { "foo": "bar" }
// To do a deep removal with property names from variables
const deep = {
foo: 'bar',
c: {
x: 1,
y: 2
}
};
const parentKey = 'c';
const childKey = 'y';
// Remove the 'c' element from original
const { [parentKey]: parentValue, ...noChild } = deep;
// Remove the 'y' from the 'c' element
const { [childKey]: removedValue, ...childWithout } = parentValue;
// Merge back together
const withoutThird = { ...noChild, [parentKey]: childWithout };
console.log(withoutThird); // Will be { "foo": "bar", "c": { "x": 1 } }
I find ES5 array methods like filter, map and reduce useful because they always return new arrays or objects. In this case I'd use Object.keys to iterate over the object, and Array#reduce to turn it back into an object.
return Object.assign({}, state, {
c: Object.keys(state.c).reduce((result, key) => {
if (key !== 'y') {
result[key] = state.c[key];
}
return result;
}, {})
});
You can use _.omit(object, [paths]) from lodash library
path can be nested for example: _.omit(object, ['key1.key2.key3'])
Just use ES6 object destructuring feature
const state = {
c: {
x: '42',
y: '43'
},
}
const { c: { y, ...c } } = state // generates a new 'c' without 'y'
console.log({...state, c }) // put the new c on a new state
That's because you are copying the value of state.c to the other object. And that value is a pointer to another javascript object. So, both of those pointers are pointing to the same object.
Try this:
let newState = Object.assign({}, state);
console.log(newState == state); // false
console.log(newState.c == state.c); // true
newState.c = Object.assign({}, state.c);
console.log(newState.c == state.c); // now it is false
delete newState.c.y;
You can also do a deep-copy of the object. See this question and you'll find what's best for you.
How about this:
function removeByKey (myObj, deleteKey) {
return Object.keys(myObj)
.filter(key => key !== deleteKey)
.reduce((result, current) => {
result[current] = myObj[current];
return result;
}, {});
}
It filters the key that should be deleted then builds a new object from the remaining keys and the initial object. The idea is stolen from Tyler McGinnes awesome reactjs program.
JSBin
function dissoc(key, obj) {
let copy = Object.assign({}, obj)
delete copy[key]
return copy
}
Also, if looking for a functional programming toolkit, look at Ramda.
As of 2019, another option is to use the Object.fromEntries method. It has reached stage 4.
const newC = Object.fromEntries(
Object.entries(state.c).filter(([key]) => key != 'y')
)
const newState = {...state, c: newC}
The nice thing about it is that it handles integer keys nicely.
You may use Immutability helper in order to unset an attribute, in your case:
import update from 'immutability-helper';
const updatedState = update(state, {
c: {
$unset: ['y']
}
});
It's easy with Immutable.js:
const newState = state.deleteIn(['c', 'y']);
description of deleteIn()
Here's an easy 1-liner you can use that allows you to partially apply the prop you want to remove. This makes it easy to pass to Array.map.
const removeProp = prop => ({ [prop]: _, ...rest }) => ({ ...rest })
Now you can use it like this:
const newArr = oldArr.map(removeProp('deleteMe'))
The issue you are having is that you are not deep cloning your initial state. So you have a shallow copy.
You could use spread operator
const newState = { ...state, c: { ...state.c } };
delete newState.c.y
Or following your same code
let newState = Object.assign({}, state, { c: Object.assign({}, state.c) });
delete newState.c.y
I normally use
Object.assign({}, existingState, {propToRemove: undefined})
I realise this isn't actually removing the property but for almost all purposes 1 its functionally equivalent. The syntax for this is much simpler than the alternatives which I feel is a pretty good tradeoff.
1 If you are using hasOwnProperty(), you will need to use the more complicated solution.
I use this pattern
const newState = Object.assign({}, state);
delete newState.show;
return newState;
but in book i saw another pattern
return Object.assign({}, state, { name: undefined } )
utility ;))
const removeObjectField = (obj, field) => {
// delete filter[selectName]; -> this mutates.
const { [field]: remove, ...rest } = obj;
return rest;
}
action type
const MY_Y_REMOVE = 'MY_Y_REMOVE';
action creator
const myYRemoveAction = (c, y) => {
const result = removeObjectField(c, y);
return dispatch =>
dispatch({
type: MY_Y_REMOVE,
payload: result
})
}
reducer
export default (state ={}, action) => {
switch (action.type) {
case myActions.MY_Y_REMOVE || :
return { ...state, c: action.payload };
default:
return state;
}
};
As hinted in some of the answers already, it's because you are trying to modify a nested state ie. one level deeper. A canonical solution would be to add a reducer on the x state level:
const state = {
a: '1',
b: '2',
c: {
x: '42',
y: '43'
},
}
Deeper level reducer
let newDeepState = Object.assign({}, state.c);
delete newDeepState.y;
Original level reducer
let newState = Object.assign({}, state, {c: newDeepState});
Use a combination of Object.assign, JSON.parse and JSON.stringify
const obj1 = { a: "a", b: "b" };
const obj2 = { c: "c", a: undefined };
const merged = Object.assign({}, obj1, obj2);
const sanitized = JSON.parse(JSON.stringify(merged));
console.log(sanitized); // -> { b: "b", c: "c" }

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