Im having trouble creating an array that contains unique subset of a larger array, please help!
Original Array allMembers (6)[{},{},{},{},{},{}]
allMembers Payload: 0:{id:1, name: Alex} 1:{id:2, name: James} 2:{id:3, name: Bob} 3:{id:4, name: lara} 4:{id:5, name: Dan} 5:{id:6, name: Jes}
Second array uniqueMembers (3)[{},{},{}]
uniqueMembers Payload: 0:{id:1, name: Alex} 1:{id:2, name: James} 2:{id:3, name: Bob}`
what I'm looking for is to find the users that are in allMembers but not in uniqueMembers
so my desired new array output would be the following array resultArray
resultArray (3)[{},{},{}]
resultArray Payload: 0:{id:4, name: lara} 1:{id:5, name: Dan} 2:{id:6, name: Jes}
My attempt
for(let m=0; m<allMembers.length;m++)
{
console.log('Testing include statement', uniqueMembers.includes(allMembers[m])) //output always false
if(uniqueMembers.includes(allMembers[m]))
{
console.log('ITS ALREADY IN: ', allMembers[m])
}else{
this.setState((prevState) => ({
resultArray: [...prevState.resultArray, allMembers[m]]
}));
console.log('ITS NOT IN: ', allMembers[m])
}
}// resultArray ends up the same as allMembers :(
Any feedback on how I can get the desired resultArray values would be appreciated!
Build an associative array to efficiently lookup if a member should be filtered out.
lookup = {}
for (const um uniqueMembers)
lookup[um.id] = 1;
resultArray = allMembers.filter( mem => !lookup.hasOwnProperty(mem) );
Two solutions posted after this one suggested using filter and some. Those solutions are O(N2). This one is should be O(N), which is way better.
If your unique array is very huge as well, convert unique array to one set first, it will save time to loop the unique array to check the match.
Then uses Array.filter to get the not in unique elements.
let all = [{id:1, name: 'Alex'}, {id:2, name: 'James'},{id:3, name: 'Bob'},{id:4, name: 'lara'},{id:5, name: 'Dan'} ,{id:6, name: 'Jes'}]
let unique = [{id:2, name: 'James'},{id:3, name: 'Bob'}]
function getNotInUnique(src, target) {
let uniqueSet = new Set(target.map(member => member.id))
return src.filter(member => !uniqueSet.has(member.id))
}
console.log(getNotInUnique(all, unique))
You can use filter along with some.
const allMembers = [
{id:1, name: 'Alex'},{id:2, name: 'James'},{id:3, name: 'Bob'}, {id:4, name: 'lara'}, {id:5, name: 'Dan'}, {id:6, name: 'Jes'}
];
const uniqueMembers = [
{id:1, name: 'Alex'},{id:2, name: 'James'},{id:3, name: 'Bob'}
];
const res = allMembers.filter(m => !uniqueMembers.some(({id})=>m.id===id));
console.log(res);
Related
Im new in react js and I get a problem with my array... I want to return a value of my array that have contain name and adress .and all value are string thi is my data that I need
name :123,
adress:12569
const array = [
0: [ 'name','123' ],
1: [ 'adress','12569'],
2: ['family','4'],
];
You can run loop on the array and assign key-value for each of the array items.
const array = [
['name', '123'],
['adress', '12569'],
['family', '4'],
];
const res = {};
array.forEach((item) => {
res[item[0]] = item[1];
})
console.log(res);
In this case, you should use an Object.
const foo = {
name: '123',
adress: 'bar',
family: '4',
}
So, to access the propertys:
console.log(foo.name); // 123
console.log(foo.adress); // bar
console.log(foo.family); // 4
But if you are getting this information as an array, you can always transform it into an object.
It would make more sense for that data to be combined into a single object rather than a series of nested arrays, and then use find to locate the object that matches the query.
const data = [
{ name: 'Bob', address: '999 Letsbe Avenue', family: 4 },
{ name: 'Sally', address: '8 Treehouse Lane', family: 0 },
{ name: 'Joan', address: '85 Long Terrace', family: 6 }
];
// Accepts the data array, and a query object
function findFamily(data, query) {
// Iterate through the data array to `find`
return data.find(obj => {
// Split the query into key/value pairs
const queryEntries = Object.entries(query);
// And return only those objects where the
// object key/value matches the query key/value
return queryEntries.every(([ key, value ]) => {
return obj[key] === value;
});
// And if there are no matches return 'No match'
}) || 'No match';
}
console.log(findFamily(data, {
name: 'Bob',
address: '999 Letsbe Avenue',
family: 0
}));
console.log(findFamily(data, {
address: '999 Letsbe Avenue',
family: 4
}));
console.log(findFamily(data, {
name: 'Sally'
}));
Additional documentation
every
Destructuring assignment
Object.entries
Today, I'm trying to get the list of javascript index based from the selected data id that I have.
I'm following this guide from https://buefy.org/documentation/table/#checkable where it needs something like this: checkedRows: [data[1], data[3]] to able to check the specific row in the table.
What I need to do is to check the table based from my web API response.
I have this sample response data.
response.data.checkedRows // value is [{id: 1234}, {id: 83412}]
and I have the sample data from the table.
const data = [{
id: 1234,
name: 'Jojo'
},{
id: 43221,
name: 'Jeff'
},{
id: 83412,
name: 'Kacey'
}]
So basically, I need to have something, dynamically, like this: checkedRows: [data[0], data[2]] because it matches the data from the response.data.checkedRows
So far, I tried using forEach
let selectedIndex = [];
response.data.checkedRows.forEach((d) => {
this.data.forEach((e) => {
if (d.id=== e.id) {
// need the result to be dynamic depending on the response.data.checkedRows
this.checkedRows = [data[0], data[2]]
}
});
});
I'm stuck here because I'm not sure how can I get the index that matches the selected checkedRows from response.
Any help?
Map the response checkedRows, and in the callback, .find the matching object in the array:
const checkedRows = [{id: 1234}, {id: 83412}];
const data = [{
id: 1234,
name: 'Jojo'
},{
id: 43221,
name: 'Jeff'
},{
id: 83412,
name: 'Kacey'
}];
const objs = checkedRows.map(({ id }) => (
data.find(obj => obj.id === id)
));
console.log(objs);
If there are a lot of elements, you can use a Set of the IDs to find instead to decrease the computational complexity:
const checkedRows = [{id: 1234}, {id: 83412}];
const data = [{
id: 1234,
name: 'Jojo'
},{
id: 43221,
name: 'Jeff'
},{
id: 83412,
name: 'Kacey'
}];
const ids = new Set(checkedRows.map(({ id }) => id));
const objs = data.filter(obj => ids.has(obj.id));
console.log(objs);
I am trying to create a new object based off an existing array. I want to create a new object that show below
{ jack: 'jack', content: 'ocean'},
{ marie: 'marie', content: 'pond'},
{ james: 'james', content: 'fish biscuit'},
{paul: 'paul', content: 'cake'}
const words = ['jack','marie','james','paul']
const myUsers = [
{ name: 'jack', likes: 'ocean' },
{ name: 'marie', likes: 'pond' },
{ name: 'james', likes: 'fish biscuits' },
{ name: 'paul', likes: 'cake' }
]
const usersByLikes = words.map(word => {
const container = {};
container[word] = myUsers.map(user => user.name);
container.content = myUsers[0].likes;
return container;
})
I am not getting the correct object, but instead it returns a list.
[ { jack: [ 'shark', 'turtle', 'otter' ], content: 'ocean'}, { marie: [ 'shark', 'turtle', 'otter' ], content: 'ocean' },
{ james: [ 'shark', 'turtle', 'otter' ], content: 'ocean' },
{ paul: [ 'shark', 'turtle', 'otter' ], content: 'ocean'} ]
What is the role of words array? I think the below code will work.
const result = myUsers.map(user => ({
[user.name]: user.name,
content: user.likes
}));
console.log('result', result);
In case, if want to filter the users in word array then below solution will work for you.
const result = myUsers.filter(user => {
if (words.includes(user.name)) {
return ({
[user.name]: user.name,
content: user.likes
})
}
return false;
});
You can achieve your need with a single loop.
The answer #aravindan-venkatesan gave should give you the result you are looking for. However important to consider:
When using .map() javascript returns an array of the same length, with whatever transformations you told it to inside map().
If you want to create a brand new object, of your own construction. Try using .reduce(). This allows you to set an input variable, i.e: object, array or string.
Then loop over, and return exactly what you want, not a mapped version of the old array.
See here for more details:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce
I'm trying to get the key of these json objects in order to create a new object with extra filed to create table headers in a React app. JSON data:
let example = [
{
id: 1,
city: 'New York',
},
{
id: 2,
city: 'Paris',
},
]
The function:
getKeys() {
return example.map((key) => {
return {
cityName: key, // gets the whole array
capital: false,
};
});
}
I tries Object.keys( example);, it returns integers; 0, 1.
How can I get the keys in this case? Thanks.
You are trying to map the keys for an array since example is an array. If the data are consistent throughout the array get the first element example[0] and do Object.keys().
So Object.keys(example[0])
There's no need to get the keys if you just want to add a property to the items in the array. I think there's a misunderstanding about .map, which gives you a single item/object in the array, not the keys.
Something like this perhaps?
let example = [{
id: 1,
city: 'New York',
}, {
id: 2,
city: 'Paris',
}];
const modifiedArray = function(arr) {
return arr.map(item => {
return {
id: item.id,
cityName: item.city,
capital: false,
};
})
}
const newArray = modifiedArray (example);
console.log(newArray )
I'm using a nested array with the following structure:
arr[0]["id"] = "example0";
arr[0]["name"] = "name0";
arr[1]["id"] = "example1";
arr[1]["name"] = "name1";
arr[2]["id"] = "example2";
arr[2]["name"] = "name2";
now I'm trying to get a nested Json Object from this array
arr{
{
id: example0,
name: name00,
},
{
id: example1,
name: name01,
},
{
id: example2,
name: name02,
}
}
I tought it would work with JSON.stringify(arr); but it doesen't :(
I would be really happy for a solution.
Thank you!
If you are starting out with an array that looks like this, where each subarray's first element is the id and the second element is the name:
const array = [["example0", "name00"], ["example1", "name01"], ["example2", "name02"]]
You first need to map it to an array of Objects.
const arrayOfObjects = array.map((el) => ({
id: el[0],
name: el[1]
}))
Then you can call JSON.stringify(arrayOfObjects) to get the JSON.
You need to make a valid array:
arr = [
{
id: 'example0',
name: 'name00',
},
{
id: 'example1',
name: 'name01',
},
{
id: 'example2',
name: 'name02',
}
];
console.log(JSON.stringify(arr));
Note that I am assigning the array to a variable here. Also, I use [] to create an array where your original code had {}.