I need to detect an object in an array with its Id.
My first array looks like that:
{ [id: 9, name: 'abc'], [id: 2, name 'def'], [id: 40, name: 'gh'] } (Id & name),
while that other array is:
{ [class: 'physics', Tid: 9], [class: 'computer science', Tid: 9], [class: 'Biology', Tid: 40] }.
I need to match the parameter "name" from the first array by its ID to its "class" (for example, "physics" relates to Tid=9 which is "abc" and "Biology" relates to Tid=40 which is "gh").
How can I elegantly do so without changing the way the data comes? (It comes from a database with ASP.NET web service in JSON)
You could use $http.get() which has success and error callback functions, which returns a promise object. Using this, you can setup a condition to map the id and get your desired result.
Something like this.
var myObject1 = {};
var myArray1 = [];
var myObject2 = {};
var myArray2 = [];
$http.get('json-file')
.success(function(data)) {
myObject1.myArray1 = data;
}
$http.get('json-file')
.success(function(data)) {
myObject2.myArray2 = data;
}
/* inside a loop if required */
if (myObject1.myArray1[index].id == myObject2.myArray2[index].Tid) {
/* perform logic */
}
This code would be present inside a service or a controller.
Haven't tested it so unsure of the syntax but promise objects are the way to go.
Hope this helps.
This returns an array of arrays. Each array in the array contains two objects matched by id === Tid. As far as I can tell that's what you want.
(Note that I think you provided broken sample arrays, I adjusted and scrambled the numbers around so you could see it work more clearly).
var arr1 = [ {id: 9, name: 'abc'}, {id: 2, name: 'def'}, {id: 40, name: 'gh'} ];
var arr2 = [ {class: 'physics', Tid: 2}, {class: 'computer science', Tid: 40}, {class: 'Biology', Tid: 9} ];
var arrFinal = arr1.map ( function ( d ) {
var matched = arr2.find ( function ( obj ) {
return obj.Tid === d.id;
} );
return [ d, matched ];
} );
If you iterate arrFinal you'll see it contains the matched objects.
Related
I have two array:
for example:
arraySelectedItems = [{id: 1, name: "item1"}, {id: 2, name: "item2"}]
arraySavedItems = [{id: 1, name: "item1"}, {id: 2, name: "item2"}]
now I need to check if there is some item in arraySavedItems that is not present in arraySelectedItems, and in this case I'll go to populate another array called arrayDeletedItems.
If the two arrays have the same items I don't need to populate the arrayDeletedItems.
So I have tried with this code:
arraySavedItems.filter((itemSaved) => !arraySelectedItems.find((itemSel) => {
if (itemSaved.id !== itemSel.id) {
arrayDeletedItems.push(itemSaved)
}
}
))
So with this data:
arraySelectedItems = [{id: 1, name: "item1"}, {id: 2, name: "item2"}]
arraySavedItems = [{id: 1, name: "item1"}, {id: 2, name: "item2"}]
I'll expect that arrayDeletedItems will be:
arrayDeletedItems = []
Instead whit this data for example:
arraySelectedItems = [{id: 1, name: "item1"}]
arraySavedItems = [{id: 1, name: "item1"}, {id: 2, name: "item2"}]
I'll expect that arrayDeletedItems will be:
arrayDeletedItems = [{id: 2, name: "item2"}]
With my code I receive and arrayDeletedItems that has the all values:
arrayDeletedItems = [{id: 1, name: "item1"}, {id: 2, name: "item2"}]
Consider this generic function:
function difference(a, b, keyFn) {
let keys = new Set(a.map(keyFn))
return b.filter(obj => !keys.has(keyFn(obj)))
}
//
selectedItems = [{id: 1, name: "item1"}, {id:4}]
savedItems = [{id: 1, name: "item1"}, {id: 2, name: "item2"}, {id:3}, {id:4}]
result = difference(selectedItems, savedItems, obj => obj.id)
console.log(result)
You can use the .includes() method on an array to check whether a value is contained in it (see the documentation for more information).
Now we can just filter the array of saved items to find only ones that aren't contained by the selected items array.
arrayDeletedItems = arraySavedItems.filter((itemSaved) =>
!arraySelectedItems.includes(itemSaved)
)
As #owenizedd points out in the comments, this only works for primitive data types where a shallow equality check is sufficient. A more robust approach can be used with the .reduce() method and a custom equality check. For example, lodash's isEqual() does a deep comparison for equality. You would have to import the module for this. Unfortunately there is no native deep equality check in JavaScript currently (workarounds like JSON.stringify() to then compare the string representations have various downsides).
arrayDeletedItems = arraySavedItems.filter((itemSaved) =>
!arraySelectedItems.reduce((previous, current) =>
previous || _.isEqual(current, itemSaved)
)
)
Note that passing previous as the first argument to the 'or' operator (||) means we can benefit from lazy evaluation - once a hit has been found, the second half of the statement does not need to be evaluated any more.
To solve this problem, since we have id we can utilize it.
You need a key that is unique. so id commonly known will have unique value.
So my approach, find items that is not exist in B array but in A array, and find items that exist in B but not in A array.
This approach not be the fastest, but the findDiff is reusable.
const a = [....];
const b = [....];
const findDiff = (source, target) => {
return source.filter((sourceItem, index) => {
const isInTarget = target.findIndex(targetItem => targetItem.id === sourceItem.id)
return isInTarget === -1
})
}
const difference = findDiff(a,b).concat(findDiff(b,a)); //result
Sorry for the basic question and bad lexicon, I am (very) new to javascript. I have an array of data and I would like to create a subset of that data, based on selected columns. The first few rows of my data, for example:
0: {ID: 3607, Name: 'Alamo', Funds: 52933955,
Revenues: 9160109, BAT: 5, …}
1: {ID: 3539, Name: 'Alvin', Funds: 6128147,
Revenues: 964083, BAT: 0, …}
2: {ID: 3540, Name: 'Amarillo', Funds: 12450969,
Revenues: 1716038, BAT: 0, …}
I want to create a new array from columns 0, 1, 2, and 4 (ID, Name, Funds, and BAT). In the code below, toolData is the array created from the original dataset (toolData.json), and tableData is the array I'm trying to create from the selected data. selections contains the column numbers I want to pull into the new array.
var getData = () => axios.get('toolData.json')
.then(res => res.data)
.then(data => {
var toolData = data;
console.log(toolData);
var tableData = [];
var selections = [0,1,2,4];
for (i=0; i < toolData.length; i++)
{
tableData[i] = toolData[i];
for (j=0; selections.length; j++)
{
k = selections[j],
tableData[i][j] = toolData[i][k]
}
}
console.log(tableData);
This particular code snippet doesn't work at all, I'm assuming I've created an infinite loop somehow. If I comment out tableData[i] = toolData[i]; then that problem resolves, but the code still doesn't work. console.log(toolData); gives me what I'm looking for (the full panel of data), but console.log(tableData); gives the error:
javascript.js:42 Uncaught (in promise) TypeError: Cannot set properties of undefined (setting '0')
at javascript.js:42
Ultimately I would like the user to be able to choose the columns they want to include in the new array, but before I can figure that puzzle out I need to solve this one.
Well, it seems from what you're saying is that every index in the array is an object.. arr[0][0]==undefined but arr[0]['ID']==3607
function newSubset(arr,dataToSelect){
//arr is the fetched array, dataToSelect is an array of the keys(like ID,Name...) that you want from the array
return arr.map(obj=>{
var toReturn={} //object that would give each desired key for each part in arr
dataToSelect.forEach(key=>toReturn[key]=obj[key]) //placing wanted keys in toReturn
return toReturn
})
}
//usage
var getData = () => axios.get('toolData.json')
.then(res => res.data)
.then(data => {
var wantedKeys=["ID","Name","Funds","BAT"]
console.log(newSubset(data,wantedKeys))
//rest of your code here
LIVE EXAMPLE
var dataArray=[{ID: 3607, Name: 'Alamo', Funds: 52933955, Revenues: 9160109, BAT: 5}, {ID: 3539, Name: 'Alvin', Funds: 6128147, Revenues: 964083, BAT: 0}, {ID: 3540, Name: 'Amarillo', Funds: 12450969, Revenues: 1716038, BAT: 0}]
function newSubset(arr,dataToSelect){
//arr is the fetched array, dataToSelect is an array of the keys(like ID,Name...) that you want from the array
return arr.map(obj=>{
var toReturn={} //object that would give each desired key for each part in arr
dataToSelect.forEach(key=>toReturn[key]=obj[key]) //placing wanted keys in toReturn
return toReturn
})
}
console.log(newSubset(dataArray,["ID","Name","Funds","BAT"]))
The data is a JSON object. It is not indexed by numbers but rather by names.
It's also recommend to use the built-in map function for this.
const tableData = toolData.map(row => ({
ID: row.ID,
Name: row.Name,
Funds: row.Funds,
BAT: row.BAT
}));
If you want the new toolData array to contain arrays instead of objects, you can instead do:
const tableData = toolData.map(row => [
row.ID,
row.Name,
row.Funds,
row.BAT
]);
I have two arrays like so
data = [{id: 1, name: apple},
{id: 2, name: mango},
{id: 3, name: grapes},
{id: 4, name: banana}]
data2 =[{id: 1, name: apple},
{id: 3, name grapes}]
My Expected result would be:
[{ id: 2, name: mango},
{id:4, name: banana}]
My code is
let finalData =[];
data.forEach(result => {
data2.find(datum => {
if(datum['id'] === result['id]{
finalData.push(result);
}
})
})
I am getting wrong result. What is the simplest code or library that I can use?
Your sample data doesn't make sense, but assuming you mean that all data items that have matching IDs also have matching names and also assuming you want a set of all items where the IDs are the same in the two sets of data, you could use a Set to keep track of which IDs are present in one array then filter the second array by those that have their IDs in the set:
const idsInFirst = new Set(data.map(d => d.id));
const intersection = data2.filter(d => idsInFirst.has(d.id));
The reason why an intermediate Set structure is used is because it allows O(1) lookups after a one-time scan, which is more efficient than repeatedly scanning the first array over and over.
If you meant to say you wanted a difference between data sets (items excluded from data that are in data2), you'd want to negate/inverse things a bit:
const idsToExclude = new Set(data2.map(d => d.id));
const difference = data.filter(d => !idsToExclude.has(d.id));
Edit
After your clarifying edit, it's that second block of code that you'll want.
I would say a good way to do that is filtering your longest array using a function that will validate if the object id is present in both arrays. Check this example:
const data = [
{id: 1, name: 'apple'},
{id: 2, name: 'mango'},
{id: 3, name: 'grapes'},
{id: 4, name: 'banana'}
]
const data2 =[
{id: 1, name: 'apple' },
{id: 3, name: 'grapes' }
]
const longest = data.length > data2.length ? data : data2;
const shortest = data.length <= data2.length ? data : data2;
const finalData = longest.filter( obj => !shortest.find( o => o.id === obj.id ) )
console.log(finalData)
Good luck!
I would like to make a deep copy of the below array. And the result should observe only the count property.
data = [{
id: 1,
code: 'ABC',
count: ko.observable(0)
},{
id: 2,
code: 'JKL',
count: ko.observable(5)
},{
id: 3,
code: 'QWE',
count: ko.observable(1)
}]
I tried ko.mapping.fromJS(ko.mapping.toJS(data)); but id and code was also converted to observables.
Currently I am using the below code to get the expected result.
var obj = ko.mapping.toJS(data);
var result = [];
obj.forEach(function(o){
var obs = ko.mapping.fromJS(o, {
'observe': "count"
});
result.push(obs);
});
// result will give the expected result
Here I have used forEach to loop each object in the data array. Is there a way to avoid the forEach loop ? or How to observe only the count property in array of object.
You can avoid the forEach as well as observe only count like this:
var result = ko.mapping.fromJS(data, {observe: 'count'});
console.log(result());
Edit:
According to the docs, we don't even need to mention ko.observable in our data. It should simply pick that up based on our 'observe' parameter. So maybe you might want to modify your data like this:
var data = [{
id: 1,
code: 'ABC',
count: 0
}, {
id: 2,
code: 'JKL',
count: 5
}, {
id: 3,
code: 'QWE',
count: 1
}];
And then, using forEach,
var result = [];
data.forEach(function(o){
result.push(ko.mapping.fromJS(o, {observe:'count'}));
});
console.log(result);
It's up to you, which method you would prefer to use.
var array1 = [{Age: 24, Name: "Test", StudentID: 101, Checked: false}, {Age:25, Name: "Test", StudentID: 102, Checked: false}];
var array2 = [{ID: 101}];
If any element in array1 has a property of StudentID that is equal to an ID property present in array2 I'd like to set the Checked property in array1 to true.
Any tips? I'd like to do this without writing nested _.each statements.
This is my first take; however, I believe _.some performs an interation anyway.
_.each($scope.array1, function(element1) {
if(_.some($scope.array2, { ID: element1.ID })) {
element1.Checked = true;
}
});
You''ll have to use two loops, since you have two arrays of random length. But you don't have to nest them. Create a map from the array of IDs and then check the index.
var availableIDs = array2.map(function ( item ) { return item.ID; });
array1.forEach(function ( item ) {
if (availableIDs.indexOf(item.StudentID) !== -1) item.Checked = true;
});
Using lodash, use a sequence in which you create a map of items in array1, using _.indexBy(). Create an array of ids from array2 using _.pluck(), and use them with _.at() to get the selected items. Iterate the returned objects using _.forEach() to set the Checked property to true, and .commit() to apply the changes:
function checkById(items, selected) {
_(items) // start chained sequence
.indexBy('StudentID') // create a map of student objects by ids
.at(_.pluck(selected, 'ID')) // create an array of IDs from the objects in the selected array
.forEach(function(item) { // change the items Checked to true
item.Checked = true;
})
.commit(); // executes the chained sequence
}
var array1 = [{
Age: 24,
Name: "Test1",
StudentID: 101,
Checked: false
}, {
Age: 25,
Name: "Test2",
StudentID: 102,
Checked: false
}, {
Age: 22,
Name: "Test3",
StudentID: 103,
Checked: false
}, {
Age: 28,
Name: "Test4",
StudentID: 104,
Checked: false
}];
var array2 = [{
ID: 101
}, {
ID: 104
}];
checkById(array1, array2);
console.table(array1);
document.getElementById('demo').innerText = JSON.stringify(array1, null, ' ');
<script src="https://cdn.jsdelivr.net/lodash/3.10.1/lodash.min.js"></script>
<pre id="demo"></pre>
using a simple mapping function you can compose an easy search through all objects
var array1 = [{Age: 24, Name: "Test", StudentID: 101, Checked: false}, {Age:25, Name: "Test", StudentID: 102, Checked: false}];
var array2 = [{ID: 101}];
function search(studentList,searchQuery) {
var results = [];
studentList.forEach(function(student,sIndex) {
searchQuery.forEach(function(search,qIndex) {
if(search.ID == student.StudentID) {
results.push(student);
}
});
})
return results;
}
search(array1,array2);
what the forEach function does is iterate over each element, passing along the object of the index it's iterating, and the index that object is at.
By having a double nested map it's easy to iterate over the objects and then compare them according to the rules you define.
Then by using a scoped variable you can push matching values into that array, giving you a nice, neat clean result to return.
Now please mind, this is not the most efficient way to handle this. You could do a test which arary is longest and have that one iterate the least time.
So if there are more students than search parameters iterate the students once. If there are more search parameters than students, iterate the search paramateters once.
also you could chooose to 'prefilter" the arrays by sorting them on the index you wish to sort on, skip the ones you don't need by simple min/max exclusion and such.
But you'd be better off using a database query for searching with large quantities of data.
But if you only have a dataset of about a 1000 or so this will suffice.
Try this snippet:
_.each(array1, function (el) {
el.Checked = !!(JSON.stringify(array2).indexOf(el.StudentID) + 1) || el.Checked;
});
Or, you can do without lo-dash.js(with pure JavaScript)
var array1 = [{Age: 24, Name: "Test", StudentID: 101, Checked: false}, {Age:25, Name: "Test", StudentID: 102, Checked: false}];
var array2 = [{ID: 101}];
var students = array1.filter(function(data){
var isTrue = !!(JSON.stringify(array2).indexOf(data.StudentID)+1);
data.Checked = isTrue || data.Checked;
return isTrue;
})
console.log(students)