I have a working function that appends an array of objects customData to the end of another array of objects testData. If an object with the same property name value appears in both arrays, then the testData object is removed and replaced with the customData object in the resulting array. The customData object takes on the order of the previous testData object.
This is my attempt however, I'm wondering if there is a better way of doing this which is also easy to read (es6)?
Thanks
https://codesandbox.io/s/recursing-river-bdp5k?file=/src/App.js
export default function App() {
const testData = [
{ display: "1", name: "TEST1" },
{ display: "2", name: "TEST2" }
];
const customData = [
{ display: "CUSTOM_1", name: "TEST1", custom: "YES" },
{ display: "CUSTOM_3", name: "TEST3", custom: "YES" }
];
let i = 0;
const newTestData = testData;
let newCustomData = customData;
while (i < customData.length) {
const view = customData[i];
const index = testData.findIndex(x => x.name === view.name);
if (index >= 0) {
newTestData[index] = customData[i];
newCustomData.splice(i, 1);
}
i += 1;
}
const concatData = newTestData.concat(newCustomData);
console.log(concatData)
return null;
}
Array#concat does not mutate the arrays, there's no need to assign them to new variables (which doesn't copy the arrays anyway). If you're seeking to use concise ES6 code, skip the while loop - there are numerous equivalents. Here's one example:
You don't define "better way" but I'll interpret it to mean "most optimized for performance and readability". In the below approach I use one pass to populate a map, and another pass to overwrite the map entries with customData where needed, and finally a Object.values() (technically a third pass) to produce the results. This is O(n) (no nested loops) versus your O(n^2) implementation.
const testData = [
{ display: "1", name: "TEST1" },
{ display: "2", name: "TEST2" }
];
const customData = [
{ display: "CUSTOM_1", name: "TEST1", custom: "YES" },
{ display: "CUSTOM_3", name: "TEST3", custom: "YES" }
];
let map = {};
testData.forEach(item => map[item.name] = item);
customData.forEach(item => map[item.name] = item);
const result = Object.values(map);
console.log(result);
For many cases including this one, where you have a bunch of data identified by a unique key (such as name), you really ought to be using objects to begin with. Any time you need an array, there's Object.values() and Object.keys().
Logic behind your code is correct.
This is almost the same, but without explicit loops:
const testData = [
{ display: "1", name: "TEST1" },
{ display: "2", name: "TEST2" }
];
const customData = [
{ display: "CUSTOM_1", name: "TEST1", custom: "YES" },
{ display: "CUSTOM_3", name: "TEST3", custom: "YES" }
];
Array.prototype.uniqueWith = function(comparator) {
return this.reduce((a, c, i) => {
const j = a.slice(i+1).findIndex(e => comparator(e, c));
if(j !== -1) {
a[i] = a[i+j+1];
a.splice(i+j+1, 1);
}
return a;
}, this);
}
const eqByName = (a, b) => a.name === b.name;
const result = [...testData, ...customData].uniqueWith(eqByName);
console.log(result);
Take a note that extending Array prototype may not be the best idea, so you may create separate function, which will take concatenated array as an argument.
Is this the kind of function you're looking for?
const result = App(myTestData(), myCustData());
console.log(result);
function App(testData, custData) {
// `indByName` returns index (in arr) of obj w/ matching name (or -1 if no match)
const indByName = (arr, name) =>
ind = arr.findIndex(o => o.name === name);
let custInd; // Identifier for output of `indByName`
const custDataClone = custData.slice(); // Prevents mutating `custData`
return testData.map(item => (
// Uses indByName to get index of corresponding custom item
custInd = indByName(custDataClone, item.name),
// Moves corresponding custom item into testData if appropriate
custInd > -1 ? custDataClone.splice(custInd, 1)[0] : item
// Appends remaining items from custDataClone to the new array
)).concat(custDataClone)
}
function myTestData(){
return [
{ display: "1", name: "TEST1" },
{ display: "2", name: "TEST2" }
];
}
function myCustData(){
return [
{ display: "CUSTOM_1", name: "TEST1", custom: "YES" },
{ display: "CUSTOM_3", name: "TEST3", custom: "YES" }
];
}
Related
So I currently have a bunch of objects inside an array like below. However, I'm now trying to write a function that allows me to add another key|value into the object that was added last.
My current idea is using the arrayname.length - 1 to work out the position of the object within the array.
Would I need to create a temporary array to store the new object and then set (tempArray = oldArray) at the end of the function or would I concatinate them both?
const state = [
{
userId: 1,
},
{
Name: name,
},
{
age: 52,
},
{
title: "et porro tempora",
}]
this is the current code
let objects = [];
const addParent = (ev) =>{
ev.preventDefault();
// getting the length of the objects array
let arrayLength = objects.length;
// if the length of the array is zero - empty or one then set it to default zero
// else if there is objects stored in the array minus 1 to get the array position
if(arrayLength <= 0){
arrayLength = 0;
}else{
arrayLength = objects.length - 1;
}
//make a temporary array to be able to push new parent into an existing object
var tempObjects = []
for (var index=0; index<objects.length; index++){
}
//create a new parent object key : value
let parent = {
key: document.getElementById('key').value,
value: document.getElementById('value').value
}
//push parent object key and value into object
//objects.push(parent);
}
document.addEventListener('DOMContentLoaded', () => {
document.getElementById('btn1').addEventListener('click', addParent);
});
There are multiple ways to do this.
Try this one
var objects = [{
name: "1"
}];
const addParent = (ev) => {
let parent = {
key: "some value",
value: "some value"
}
objects = Array.isArray(objects) ? objects : [];
let lastObjectIndex = objects.length - 1;
lastObjectIndex = lastObjectIndex > -1 ? lastObjectIndex : 0
objects[lastObjectIndex] = { ...objects[lastObjectIndex],
...parent
}
}
I think You want to add new value to last object of the array
Method 1
const state = [
{
userId: 1,
},
{
Name: name,
},
{
age: 52,
},
{
title: "et porro tempora",
}]
state[state.length - 1].newKey = "value"
console.log(state)
Method 2
const state = [
{
userId: 1,
},
{
Name: name,
},
{
age: 52,
},
{
title: "et porro tempora",
}]
// 1st method
state[state.length - 1] = {
...state[state.length - 1] ,
newKey : "value"
}
console.log(state)
You can probably use something like this:
const a = [
{ "a" : "a" },
{ "b" : "b" }
]
const c = a.map((obj, index) => {
if (index === a.length -1) {
return { ...obj, newProp: "newProp" }
}
return obj;
});
console.log(c)
This will add property on the last object using spread operator, you can look it up if you are new to JS but basically it will retain all the existing property and add the newProp to the object
I have an array of duplicated objects in Javascript. I want to create an array of unique objects by adding the index of occurrence of the individual value.
This is my initial data:
const array= [
{name:"A"},
{name:"A"},
{name:"A"},
{name:"B"},
{name:"B"},
{name:"C"},
{name:"C"},
];
This is expected end result:
const array= [
{name:"A-0"},
{name:"A-1"},
{name:"A-2"},
{name:"B-0"},
{name:"B-1"},
{name:"C-0"},
{name:"C-1"},
];
I feel like this should be fairly simple, but got stuck on it for a while. Can you please advise how I'd go about this? Also if possible, I need it efficient as the array can hold up to 1000 items.
EDIT: This is my solution, but I don't feel like it's very efficient.
const array = [
{ name: "A" },
{ name: "A" },
{ name: "C" },
{ name: "B" },
{ name: "A" },
{ name: "C" },
{ name: "B" },
];
const sortedArray = _.sortBy(array, 'name');
let previousItem = {
name: '',
counter: 0
};
const indexedArray = sortedArray.map((item) => {
if (item.name === previousItem.name) {
previousItem.counter += 1;
const name = `${item.name}-${previousItem.counter}`;
return { name };
} else {
previousItem = { name: item.name, counter: 0};
return item;
}
});
Currently you are sorting it first then looping over it, which may be not the most efficient solution.
I would suggest you to map over it with a helping object.
const a = [{name:"A"},{name:"A"},{name:"A"},{name:"B"},{name:"B"},{name:"C"},{name:"C"},], o = {};
const r = a.map(({ name }) => {
typeof o[name] === 'number' ? o[name]++ : o[name] = 0;
return { name: `${name}-${o[name]}` };
});
console.log(r);
Keep a counter, and if the current name changes, reset the counter.
This version mutates the objects. Not sure if you want a copy or not. You could potentially sort the array by object name first to ensure they are in order (if that's not already an existing precondition.)
const array = [
{ name: "A" },
{ name: "A" },
{ name: "A" },
{ name: "B" },
{ name: "B" },
{ name: "C" },
{ name: "C" },
];
let name, index;
for (let i in array) {
index = array[i].name == name ? index + 1 : 0;
name = array[i].name;
array[i].name += `-${index}`;
}
console.log(array);
Another way, if you don't want to sort, and don't want to mutate any objects, is to use a map and keep track of the current index for each object.
const array = [
// NOTE: I put the items in mixed up order.
{ name: "A" },
{ name: "C" },
{ name: "A" },
{ name: "B" },
{ name: "A" },
{ name: "C" },
{ name: "B" },
];
let index = {};
let next = name => index[name] = index[name] + 1 || 0;
let result = array.map(obj => ({ ...obj, name: obj.name + '-' + next(obj.name) }));
console.log(result);
My Goal:
I need to have a continuous sequence of numbers in the sequenceIndex which is a value in my object.
So when I remove a specific object the sequence index of the other objects is of course not continuous anymore. The object I remove is being checked against a specific value to see whether there are other objects in the array which share the same value (second if-statement). If so then there should be a new value set which is continuous.
The output is that the iterator in the if-statement is always the same for all objects manipulated.
From this:
const objectsArray = [
{
folder: "folderName",
documents: [
{
id: 0,
sequenceIndex: "0",
documentType: "letter"
},
{
id: 1,
sequenceIndex: "1",
documentType: "letter"
},
{
id: 2,
sequenceIndex: "2",
documentType: "letter"
},
{
id: 3,
sequenceIndex: "3",
documentType: "letter"
}
]
}
];
By removing id 1 and 2 I would like to come to this (see continuous sequenceIndex):
const desiredObjectsArray = [
{
folder: "folderName",
documents: [
{
id: 0,
sequenceIndex: "0",
documentType: "letter"
},
{
id: 3,
sequenceIndex: "1",
documentType: "letter"
}
]
}
];
My code so far:
case ActionType.RemoveDocumentInSpecificFolder:
return state.map(file => {
// if in the correct folder remove the object with the delivered id
if (file.folder=== folder) {
remove(file.documents, {
id: action.payload.documents[0].id
});
// create newObjArray from objects which share a specific value and replace the sequence index by new value
const newObjArray = file.documents.map((obj: any) => {
// if the object has the specific value create new object with new sequenceIndex
if (obj.documentType === action.payload.documents[0].documentType) {
//poor attempt to create a sequence
let i = 0;
const correctedSequenceDocObject = { ...obj, sequenceIndex: i };
i++;
return correctedSequenceDocObject;
}
return {
...obj
};
});
return {
...file,
documents: newObjArray
};
}
return file;
});
I hope someone can guide me in the right direction. I would also always appreciate a suggestion of best practice :)
Best regards
You can use filter and map something like this
const arr = [{folder: "folderName",documents: [{id: 0,sequenceIndex: "0",documentType: "letter"},{id: 1,sequenceIndex: "1",documentType: "letter"},{id: 2,sequenceIndex: "2",documentType: "letter"},{id: 3,sequenceIndex: "3",documentType: "letter"}]}];
let getInSequence = (filterId) => {
return arr[0].documents.filter(({ id }) => !filterId.includes(id))
.map((v, i) => ({ ...v, sequenceIndex: i }))
}
console.log(getInSequence([1, 2]))
As commented:
This is the classic case where .filter().map() will be useful. filter the data and then use .map((o, i) => ({ ...obj, sequenceIndex: i+1 }) )
Following is the sample:
const objectsArray = [{
folder: "folderName",
documents: [{
id: 0,
sequenceIndex: "0",
documentType: "letter"
},
{
id: 1,
sequenceIndex: "1",
documentType: "letter"
},
{
id: 2,
sequenceIndex: "2",
documentType: "letter"
},
{
id: 3,
sequenceIndex: "3",
documentType: "letter"
}
]
}];
const ignoreIds = [1, 2]
const updatedDocs = objectsArray[0].documents
.filter(({
id
}) => !ignoreIds.includes(id))
.map((doc, index) => ({ ...doc,
sequenceIndex: index
}));
console.log(updatedDocs)
Now lets cover your attempt
const newObjArray = file.documents.map((obj: any) => {
// For all the unmatching objects, you will have undefined as object as you are using `.map`
// This will make you `newObjArray: Array<IDocument | undefined>` which can break your code.
if (obj.documentType === action.payload.documents[0].documentType) {
// This will set it as 0 in every iteration making i as 0 always.
let i = 0;
const correctedSequenceDocObject = { ...obj, sequenceIndex: i };
i++;
return correctedSequenceDocObject;
}
return { ...obj };
});
An alternate with single loop:
Idea:
Create a loop using Array.reduce and pass it a blank array as list.
Add a check and inside it, push value to this list.
For sequenceIndex, fetch last element and fetch its sequenceIndex. Add one and set it again.
const newObjArray = file.documents.reduce((acc: Array<IDocument>, obj: any) => {
if (obj.documentType === action.payload.documents[0].documentType) {
const sequenceIndex: number = (!!acc[acc.length - 1] ? acc[acc.length - 1].sequenceIndex : 1) + 1;
acc.push({ ...obj, sequenceIndex });
}
return acc;
});
The solution I used now to this problem was:
let count = 0;
const newObject = file.documents.map(obj => {
if (obj.documentType === firstDocument.documentType) {
count++;
return { ...obj, sequenceIndex: count - 1 };
}
return obj;
});
Both of the provided answers were not able to handle objects which were out of interest because of the different documentType so they dropped the object. with this solution, I am checking against the last element and increasing the count if the last element was the same documentType.
I am aware of options like the spread operator and Object.assign() when it comes to converting an array to an object, however, I am having difficulty figuring out how to format the final object in the format I need.
My original array looks like this:
let propsArray = [ { id: '1' },
{ 'name.first': 'john' },
{ 'name.last': 'smith' } ]
The object I want from this data needs to look like this:
{
"id" : 1,
"name" : {
"first" : "john",
"last" : "smith"
}
}
What I've tried so far, using object.assign(), ends up adding numbers as property keys in the resulting object, which is clearly not what I'm looking for:
let finalObj = Object.assign({}, propsArray);
How can I get the resulting object formatted the way I need here?
You need a deeper look into the object and take the splitted key and reduce them by taking an object with the property or an empty object. At the end assign the value.
var data = [{ id: '1' }, { 'name.first': 'john' }, { 'name.last': 'smith' }],
result = data.reduce((r, o) => {
Object.entries(o).forEach(([k, v]) => {
var keys = k.split('.'),
last = keys.pop();
keys.reduce((q, k) => q[k] = q[k] || {}, r)[last] = v;
});
return r;
}, {});
console.log(result);
Try this:
const data = [
{
"id": "1"
},
{
"name.first": "john"
},
{
"name.last": "smith"
}
]
const result = Object.entries(Object.assign({}, ...data))
.reduce((acc,[k,v])=>{
[first, last] = k.split('.');
if (!last) {
acc[k] = v
} else {
acc[first] = acc[first] || {};
acc[first][last] = v;
}
return acc
}, {})
console.log(result);
var set = [{"color":"blue"},{"color":"green"},{"color":"red"},{"color":"green"}];
I'd like to be able to do something like a db call, set.find({"color":"green"}) and have it return an array full of objects that contain that property.
Using Array#filter, for this particular case the code would look like
var results = set.filter(function (entry) { return entry.color === "green"; });
Array#filter is not implemented in some older browsers, so see the linked article for a backward compatibility shim, or better yet get a full-fledged ES5 shim.
For the more general case, it's just a matter of extending this idea:
function findByMatchingProperties(set, properties) {
return set.filter(function (entry) {
return Object.keys(properties).every(function (key) {
return entry[key] === properties[key];
});
});
}
var results = findByMatchingProperties(set, { color: "green" });
Again, I am using ECMAScript 5 methods Object.keys and Array#every, so use an ES5 shim. (The code is doable without an ES5 shim but uses manual loops and is much less fun to write and read.)
I have used map function from jquery and I am getting selected index by passing searched key value so by using that index we will get required object from array.
var mydata = [{ name: "Ram", Id: 1 }, { name: "Shyam", Id: 2 }, { name: "Akhil", Id: 3 }];
searchKey = 2
var mydata = [{ name: "Ram", Id: 1 }, { name: "Shyam", Id: 2 }, { name: "Akhil", Id: 3 }];
searchKey = 2
var selectedData = mydata[mydata.map(function (item) { return item.Id; }).indexOf(searchKey)];
console.log(selectedData)
var selectedData = mydata[mydata.map(function (item) { return item.Id; }).indexOf(searchKey)];
console.log(selectedData)
output
{ name: "Shyam", Id: 2 }
Note: if you want to pass search key as object then
searchKey = { Id: 2 };
mydata[mydata.map(function (item) { return item.Id; }).indexOf(searchKey.Id)];
output
{ name: "Shyam", Id: 2 }
Using arrow functions with an implied return and concise body:
const results = set.filter(entry => entry.color === "green");
Another example passing in a search variable:
const searchString = 'green';
const results = set.filter(entry => entry.color === `${searchString}`);
Read more about arrow functions on
MDN
Since you've included the jQuery tag, here's one way to do it using jQuery's map:
var results = $.map( set, function(e,i){
if( e.color === 'green' ) return e;
});
The documentation states that you need to return null to remove the element from the array, but apparently this is false, as shown by the jsFiddle in the comments; returning nothing (i.e. returning undefined) works just as well.
I went with a different approach that I found to be a bit easier.
function isObjEqual(a, b) {
const x = JSON.stringify(a);
const y = JSON.stringify(b);
return x === y;
}
// Example 1
const set = [{"color":"blue"},{"color":"green"},{"color":"red"},{"color":"green"}];
const findObj1 = {"color":"green"};
const arr1 = set.filter((objInArr) => isObjEqual(objInArr, findObj1));
console.log(arr1) // [ { color: 'green' }, { color: 'green' } ]
// Example 2
const list = [{
"label": "Option 2",
"value": "option2"
},
{
"label": "Option 3",
"value": "option3"
},
{
"label": "Option 2",
"value": "option2"
}
];
const findObj2 = {
"label": "Option 2",
"value": "option2"
}
const newList = list.filter((objInArr) => isObjEqual(objInArr, findObj2));
console.log(newList) //[ { label: 'Option 2', value: 'option2' }, { label: 'Option 2', value: 'option2' } ]