I have following Plunkr which works perfectly.
https://plnkr.co/edit/WDjoEK7bAVpKSJbAmB9D?p=preview
It uses the _.differenceWith() function of lodash, in order two save all array values, which are not contained by the two arrays.
var result = _.differenceWith(data, test, _.isEqual);
Now I have two problems:
1.) In our project we use an older Lodash Version where the function differenceWith is not implemented
2.) I only need to compare one value of the array. This currently compares the complete objects. I only need to compare the id property.
This will find the objects in arr1 that are not in arr2 based on the id attribute.
var arr1 = [ { "id": "1" }, { "id": "2" }, { "id": "3" } ];
var arr2 = [ { "id": "1" }, { "id": "2" } ];
var result = arr1.filter(o1 => arr2.filter(o2 => o2.id === o1.id).length === 0);
console.log(result);
Note that this example does not require lodash.
If you want to use a different comparison instead of id, you can change the o2.id === o1.id part to a different property.
Here is a more generic solution:
var arr1 = [ { "name": "a" }, { "name": "b" }, { "name": "c" } ];
var arr2 = [ { "name": "a" }, { "name": "c" } ];
function differenceWith(a1, a2, prop) {
return a1.filter(o1 => a2.filter(o2 => o2[prop] === o1[prop]).length === 0);
}
var result = differenceWith(arr1, arr2, 'name');
console.log(result);
Related
I have a array as follows:
data = [
{
"id":1
"name":"london"
},
{
"id":2
"name":"paris"
},
{
"id":3
"name":"london"
},
{
"id":4
"name":"paris"
},
{
"id":5
"name":"australia"
},
{
"id":6
"name":"newzearland"
}
]
At runtime this array can have n number of elements. I want to group this array with respect to name attribute. All the elements with same name should be moved to a separate array. I don't know the what value can name have in advance. This is coming at runtime. For example, from above array I want final output as follows:
output:
newArray1 = [
{
"id":1
"name":"london"
},
{
"id":3
"name":"london"
}
]
newArray2 = [
{
"id":2
"name":"paris"
},
{
"id":4
"name":"paris"
}
]
newArray3 = [
{
"id":5
"name":"australia"
}
]
newArray4 = [
{
"id":6
"name":"newzearland"
}
]
How can I do that?
As Teemu has already pointed out in a comment, creating new variables to store the data is not ideal. You would have no way of knowing how many groups you've created and using variables that you can't be sure exist is not the best way to write code. Fortunately, JavaScript has objects, which can store data like this in a much cleaner way. Here's the code I've come up with:
function groupBy(arr, key) {
let res = {}
for (let element of arr) {
if (res.hasOwnProperty(element[key])) {
res[element[key]].push(element)
} else {
res[element[key]] = [element]
}
}
return res
}
This code is not the best, most efficient code ever, but it is written to be easier to understand for someone still learning. This code loops over every element in your data and checks whether our result already contains an array for elements with that name. If there's already an array for elements with that name, the current element is added to it. If there isn't one, a new one is created with the current element inside it. To do exactly what you want, you'd call this function with groupBy(data, "name") and assign it to a new variable like groupedData (THIS DOES NOT MODIFY THE DATA, IT RETURNS A NEW OBJECT OF GROUPED DATA) .
Start by getting all the unique .names, then map them to the original array filtered by each .name:
const data = [{
"id": 1, "name": "london"
},
{
"id": 2, "name": "paris"
},
{
"id": 3, "name": "london"
},
{
"id": 4, "name": "paris"
},
{
"id": 5, "name": "australia"
},
{
"id": 6, "name": "newzearland"
}
];
const newData = [...new Set(data
//Get all names in an array
.map(({name}) => name))]
//For each name filter original array by name
.map(n => data.filter(({name}) => n === name));
console.log( newData );
//OUTPUT: [newArray1, newArray2, .....]
You can get the expected result with grouping by key approach.
const data = [{"id":1,"name":"london"},{"id":2,"name":"paris"},{"id":3,"name":"london"},{"id":4,"name":"paris"},{"id":5,"name":"australia"},{"id":6,"name":"newzearland"}];
const result = Object.values(data.reduce((acc, obj) =>
({ ...acc, [obj.name]: [...(acc[obj.name] ?? []), obj] }), {}));
console.log(result);
const [newArray1, newArray2, newArray3, newArray4, ...rest] = result;
console.log('newArray1:', newArray1);
console.log('newArray2:', newArray2);
console.log('newArray3:', newArray3);
console.log('newArray4:', newArray4);
.as-console-wrapper{min-height: 100%!important; top: 0}
This question already has answers here:
Most efficient method to groupby on an array of objects
(58 answers)
Closed 3 years ago.
I have an array of objects that looks like this:
let stuff = [
{
"id": "48202847",
"name": "Doe"
},
{
"id": "17508",
"name": "Marie"
},
{
"id": "175796",
"name": "Robert"
},
{
"id": "175796",
"name": "Ronald"
},
]
What I want to get is a dictionary looking something like this:
{
"D": [{"id": "48202847", "name": "Doe"}],
"M": [{"id": "17508", "name": "Marie"}],
"R": [{"id": "175796", "name": "Robert"}, {"id": "175796", "name": "Ronald"}]
}
Notice how all the people whose name starts with "R" are listed under one key.
This is my function that creates a dictionary with the person's name as the key:
const byId = (array) =>
array.reduce((obj, item) => {
obj[item.name] = item
return obj
}, {})
But this obviously doesn't do what I want it to. I do have some ideas of how to make this possible, but they are extremely legacy and I would love to know how to do this right.
Any help is appreciated!
You need the first character, uppercase and an array for collecting the objects.
const byId = array =>
array.reduce((obj, item) => {
var key = item.name[0].toUpperCase(); // take first character, uppercase
obj[key] = obj[key] || []; // create array if not exists
obj[key].push(item); // push item
return obj
}, {});
let stuff = [{ id: "48202847", name: "Doe" }, { id: "17508", name: "Marie" }, { id: "175796", name: "Robert" }, { id: "175796", name: "Ronald" }],
result = byId(stuff)
console.log(result);
Here's a solution based on Set, map, reduce and filter:
let stuff = [{"id": "48202847","name": "Doe"},{"id": "17508","name": "Marie"},{"id": "175796","name": "Robert"},{"id": "175796","name": "Ronald"}];
let result = [...new Set(stuff.map(x => x.name[0]))]
.reduce((acc, val) => {
return acc = { ...acc,
[val]: stuff.filter(x => x.name.startsWith(val))
}
}, {});
console.log(result);
Great solution Nina! Could be made a little cleaner by utilizing the spread operator.
const byId = (array) =>
array.reduce((obj, item) => {
var key = item.name[0].toUpperCase();
return {
...obj,
[key]: obj[key] ? [...obj[key], item] : [item],
}
}, {});
Is it possible to filter an array of objects by multiple values?
E.g in the sample below can I filter it by the term_ids 5 and 6 and type car at the same time?
[
{
"id":1,
"term_id":5,
"type":"car"
},
{
"id":2,
"term_id":3,
"type":"bike"
},
{
"id":3,
"term_id":6,
"type":"car"
}
]
Definitely up for using a library if it makes it easier.
You can do it with Array.filter
var data = [{
"id": 1,
"term_id": 5,
"type": "car"
},
{
"id": 2,
"term_id": 3,
"type": "bike"
},
{
"id": 3,
"term_id": 6,
"type": "car"
}
];
var result = data.filter(function(v, i) {
return ((v["term_id"] == 5 || v["term_id"] == 6) && v.type == "car");
})
console.log(result)
The following function will help you out.
nestedFilter = (targetArray, filters) => {
var filterKeys = Object.keys(filters);
return targetArray.filter(function (eachObj) {
return filterKeys.every(function (eachKey) {
if (!filters[eachKey].length) {
return true;
}
return filters[eachKey].includes(eachObj[eachKey]);
});
});
};
Use this function with filters described as below:
var filters = {
"id": ["3"],
"term_id": ["6"],
"type": ["car","bike"]
}
Dont pass empty array. If there are no values in the array, skip that property in the filters.
The result will be filtered array.
You can do this with plain js filter() method and use && to test for both conditions.
var data = [{"id":1,"term_id":5,"type":"car"},{"id":2,"term_id":3,"type":"bike"},{"id":3,"term_id":6,"type":"car"}];
var result = data.filter(function(e) {
return [5, 6].includes(e.term_id) && e.type == 'car'
});
console.log(result);
Another way to do it is to use lodash filter + reduce.
const arr = [{"id":1,"term_id":5,"type":"car"},{"id":2,"term_id":3,"type":"bike"},{"id":3,"term_id":6,"type":"car"}];
const result = [
{term_id: 5, type: 'car'},
{term_id: 6, type: 'car'},
].reduce((prev, orCondition) => prev.concat(_.filter(arr, orCondition)), []);
console.log(result);
<script src="https://cdn.jsdelivr.net/npm/lodash#4.17.21/lodash.min.js"></script>
I'm trying to count the number of string in an array of objects using lowdb.
Here is a sample of my objects:
{
"tags": [
"test",
"test2"
]
},
{
"tags": [
"test",
"test3"
]
}
I'd like to get this:
{
test: 2,
test2: 1,
test3: 1
}
I have successfully get this doing like this:
_.each(selectAll().value(), (bookmark) => {
if (bookmark.tags.length > 0) {
_.each(bookmark.tags, (bookmarksTags) => {
if (!(bookmarksTags in tags)) {
tags[bookmarksTags] = 0
}
tags[bookmarksTags]++
})
}
})
It works but... it's ugly and I don't like it. Do you know a better and proper Lodash's way to do this?
You can use reduce() and forEach() with plain javascript.
var data = [{"tags":["test","test2"]},{"tags":["test","test3"]}]
var result = data.reduce(function(r, e) {
return (e.tags.forEach(e => r[e] = (r[e] || 0) + 1)), r
}, {})
console.log(result)
One way using Lodash:
_.countBy(_.flatMap(arr,'tags'))
Where arr is the source array
var o = [{ "tags": [ "test", "test2" ]},{ "tags": [ "test", "test3" ]}];
console.log(_.countBy(_.flatMap(o,'tags')));
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
I'm looking for a way to find any objects in one array that are not present in another array based upon that object's property. What's the best way to do this with jQuery or underscore?
Given the following example:
"array1":[
{"testProperty":"A"},
{"testProperty":"B"},
{"testProperty":"C"}
]
"array2":[
{"testProperty":"A", "User":"Smith"},
{"testProperty":"B", "User":"Smith"},
]
I would want to return the third object from array1 whose testProperty is "C" since it's not present in array2.
I was able to find several examples of this issue here on stackoverflow, but not when needing to do so using properties from those objects.
I'm not sure if this counts, but if you can use lodash instead of underscore, there is a nice function called differenceBy:
var _ = require("lodash");
var array1 = [
{"testProperty":"A"},
{"testProperty":"B"},
{"testProperty":"C"}
]
var array2 = [
{"testProperty":"A", "User":"Smith"},
{"testProperty":"B", "User":"Smith"}
]
var result = _.differenceBy(array1, array2, function(item) {
return item["testProperty"]
});
console.log(result);
A proposal in plain Javascript with a hash table for look-up.
var data = { "array1": [{ "testProperty": "A" }, { "testProperty": "B" }, { "testProperty": "C" }], "array2": [{ "testProperty": "A", "User": "Smith" }, { "testProperty": "B", "User": "Smith" }, ] },
result = data.array1.filter(function (a) {
return !this[a.testProperty];
}, data.array2.reduce(function (r, a) {
r[a.testProperty] = true;
return r;
}, Object.create(null)));
document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');
You can use filter with map
var a = {'array1': [{"testProperty":"A"}, {"testProperty":"B"}, {"testProperty":"C"}], 'array2': [{"testProperty":"A", "User":"Smith"}, {"testProperty":"B", "User":"Smith"}]};
var result = a.array1.filter(function(e) {
return a.array2.map(el => { return el.testProperty}).indexOf(e.testProperty) == -1;
});
console.log(result);
here's a version in plain es6 js using filter and some method:
array1 = [
{"testProperty":"A"},
{"testProperty":"B"},
{"testProperty":"C"}
];
array2 =[
{"testProperty":"A", "User":"Smith"},
{"testProperty":"B", "User":"Smith"},
]
var r = array1.filter(x =>
! Object.keys(x).some(z =>
array2.some(w =>
Object.keys(w).some(y => y === z && w[y] === x[z])
)));
document.write(JSON.stringify(r))
You could use underscore's reject and some to get what you want:
var result = _.reject(array1, item => _.some(array2, {testProperty: item.testProperty}));
If performance is a concern and testProperty is an unique key of the objects in array2 then you could create a hash using indexBy and check for the result using has:
var hash = _.indexBy(array2, 'testProperty');
var result = _.reject(array1, item => _.has(hash, item.testProperty));