I have an array of objects, each array has a key of name and then another array of objects:
const myArray = [ { name: "1", item: [{}] }, { name: "2", item: [{}] }, { name: "1", item: [{}] } ]
Now for example sometimes that name key will be the same, i want to be able to check if that name exists and if it does exist push the item into that array object and not into a new object.
The behaviour im getting is above but i would like:
const myArray = [ { name: "1", item: [{ item1, item2 etc }] }, { name: "2", item: [{}] }, { name: "3", item: [{}] } ]
Thanks so much in advance!
You can get the desired result using Array.reduce(), grouping by name.
If two objects in myArray share the same name, the item values are combined.
const myArray = [ { name: "1", item: [{ id: 1 }] }, { name: "2", item: [{ id: 2}] }, { name: "1", item: [{ id: 3}] } ]
const result = Object.values(myArray.reduce((acc, { name, item }) => {
acc[name] = acc[name] || { name, item: [] };
acc[name].item.push(...item);
return acc;
}, {}))
console.log('Result:', result)
.as-console-wrapper { max-height: 100% !important; }
Here's a solution using Array.prototype.reduce function.
const myArray = [ { name: "1", item: [{}] }, { name: "2", item: [{}] }, { name: "1", item: [{}] } ];
const output = myArray.reduce((acc, curr) => {
const index = acc.findIndex(pre => pre.name === curr.name);
if(index !== -1) {
acc[index].item = acc[index].item.concat(curr.item);
} else {
acc.push(curr);
}
return acc;
}, []);
console.log(output);
I have an array with duplicated entries.
I'm looking for:
removing all duplicate occurrences
And increment the val propertie off an element if we find an occurrence
here is an exemple of what I have:
const arr = [
{"id":"46","name":"Productivity","val":1},
{"id":"1","name":"test","val":1},
{"id":"43","name":"Health and Fitness","val":1},
{"id":"46","name":"Productivity","val":1},
{"id":"1","name":"test","val":1},
{"id":"46","name":"Productivity","val":1}
]
// Wanted result
const result = [
{"id":"46","name":"Productivity","val":3},
{"id":"43","name":"Health and Fitness","val":1},
{"id":"1","name":"test","val":2}
]
Here is a JsFiddle
You can easily achieve this using reduce and object destructuring.
const arr = [
{ id: "46", name: "Productivity", val: 1 },
{ id: "1", name: "test", val: 1 },
{ id: "43", name: "Health and Fitness", val: 1 },
{ id: "46", name: "Productivity", val: 1 },
{ id: "1", name: "test", val: 1 },
{ id: "46", name: "Productivity", val: 1 },
];
const result = arr.reduce((acc, curr) => {
const { id, name, val } = curr;
const isPresent = acc.find((el) => el.id === id);
if (!isPresent) acc = [...acc, { id, name, val }];
else isPresent.val = isPresent.val + val;
return acc;
}, []);
console.log(result);
I'm trying to get an array of objects into an object-format with the values as the keys of the new object.
Let's say I got this data:
const data = [
{
key: "foo",
value: "xyz",
classLabel: "Test"
},
{
key: "foo",
value: "abc",
classLabel: "Test"
},
{
key: "bar",
value: "aaa",
classLabel: "Test"
}]
And the format I want to build is like this:
const expected = {
foo: ["xyz", "abc"],
bar: ["aaa"]
}
The values are transferred to the keys and pushed into the same array for duplicate keys.
So far I only extracted the keys with:
const result = [...new Set(data.map(item => item.key))]; // ["foo", "bar"]
const data = [
{
key: "foo",
value: "xyz",
classLabel: "Test"
},
{
key: "foo",
value: "abc",
classLabel: "Test"
},
{
key: "bar",
value: "aaa",
classLabel: "Test"
}];
let expected = data.reduce((out, {key, value}) => {
out[key] = out[key] || [];
out[key].push(value);
return out;
}, {});
console.log(expected);
The following should work:
const data = [
{
key: "foo",
value: "xyz",
classLabel: "Test",
},
{
key: "foo",
value: "abc",
classLabel: "Test",
},
{
key: "bar",
value: "aaa",
classLabel: "Test",
},
];
const mapToObj = (arr) => {
let obj = {};
for (let i in arr) {
let objKey = arr[i].key;
obj[objKey]
? Object.assign(obj, { [arr[i].key]: [obj[objKey], arr[i].value] })
: Object.assign(obj, { [arr[i].key]: arr[i].value });
}
return obj;
};
console.log(mapToObj(data));
This question already has answers here:
Remove duplicates form an array
(17 answers)
Closed 5 years ago.
I have this array?
var arr = [{id:"1",Name:"Tom"},
{id:"2",Name:"Jon"},
{id:"3",Name:"Tom"},
{id:"4",Name:"Jack"}]
From array above I need to fecth all existing Names distinct.
var result = getNamesDistinct(arr);
The result should contain result is:
["Tom","Jon","Jack"];
My question is how to get all existing Names from arr distinct?
If Set is available, you can simply do
new Set(arr.map(obj => obj.Name))
(pass the set to Array.from if you need an array)
You can do it via Set object
const arr = [
{ id: "1", Name: "Tom" },
{ id: "2", Name: "Jon" },
{ id: "3", Name: "Tom" },
{ id: "4", Name: "Jack" }
];
const uniqueNames = [...new Set(arr.map(item => item.Name))];
console.log(uniqueNames);
Or you can iterate over the array and add condition to get only unique names.
const arr = [
{ id: "1", Name: "Tom" },
{ id: "2", Name: "Jon" },
{ id: "3", Name: "Tom" },
{ id: "4", Name: "Jack" }
];
const uniqueNames = arr.reduce(function(arr, item) {
if(arr.indexOf(item.Name) === -1) {
arr.push(item.Name);
}
return arr;
}, []);
console.log(uniqueNames);
you can try this
var array = [{
id: "1",
Name: "Tom"
}, {
id: "2",
Name: "Jon"
}, {
id: "3",
Name: "Tom"
}, {
id: "4",
Name: "Jack"
}]
function uniqueNames(array) {
var newArray = [];
array.forEach((value, key) => {
newArray.push(value.Name)
});
return newArray
}
var myNewArray = uniqueNames(array)
What is the best way to merge array contents from JavaScript objects sharing a key in common?
How can array in the example below be reorganized into output? Here, all value keys (whether an array or not) are merged into all objects sharing the same name key.
var array = [
{
name: "foo1",
value: "val1"
}, {
name: "foo1",
value: [
"val2",
"val3"
]
}, {
name: "foo2",
value: "val4"
}
];
var output = [
{
name: "foo1",
value: [
"val1",
"val2",
"val3"
]
}, {
name: "foo2",
value: [
"val4"
]
}
];
Here is one option:-
var array = [{
name: "foo1",
value: "val1"
}, {
name: "foo1",
value: ["val2", "val3"]
}, {
name: "foo2",
value: "val4"
}];
var output = [];
array.forEach(function(item) {
var existing = output.filter(function(v, i) {
return v.name == item.name;
});
if (existing.length) {
var existingIndex = output.indexOf(existing[0]);
output[existingIndex].value = output[existingIndex].value.concat(item.value);
} else {
if (typeof item.value == 'string')
item.value = [item.value];
output.push(item);
}
});
console.dir(output);
Here is another way of achieving that goal:
var array = [{
name: "foo1",
value: "val1"
}, {
name: "foo1",
value: [
"val2",
"val3"
]
}, {
name: "foo2",
value: "val4"
}];
var output = array.reduce(function(o, cur) {
// Get the index of the key-value pair.
var occurs = o.reduce(function(n, item, i) {
return (item.name === cur.name) ? i : n;
}, -1);
// If the name is found,
if (occurs >= 0) {
// append the current value to its list of values.
o[occurs].value = o[occurs].value.concat(cur.value);
// Otherwise,
} else {
// add the current item to o (but make sure the value is an array).
var obj = {
name: cur.name,
value: [cur.value]
};
o = o.concat([obj]);
}
return o;
}, []);
console.log(output);
2021 version
Using reduce to aggregate data.
Using logical nullish assignment only assigns if acc[name] is nullish (null or undefined).
Using Array.isArray to determines whether the passed value is an Array.
var arrays = [{ name: "foo1",value: "val1" }, {name: "foo1", value: ["val2", "val3"] }, {name: "foo2",value: "val4"}];
const result = arrays.reduce((acc, {name, value}) => {
acc[name] ??= {name: name, value: []};
if(Array.isArray(value)) // if it's array type then concat
acc[name].value = acc[name].value.concat(value);
else
acc[name].value.push(value);
return acc;
}, {});
console.log(Object.values(result));
Using lodash
var array = [{name:"foo1",value:"val1"},{name:"foo1",value:["val2","val3"]},{name:"foo2",value:"val4"}];
function mergeNames (arr) {
return _.chain(arr).groupBy('name').mapValues(function (v) {
return _.chain(v).pluck('value').flattenDeep();
}).value();
}
console.log(mergeNames(array));
Here is a version using an ES6 Map:
const arrays = [{ name: "foo1",value: "val1" }, {name: "foo1", value: ["val2", "val3"] }, {name: "foo2",value: "val4"}];
const map = new Map(arrays.map(({name, value}) => [name, { name, value: [] }]));
for (let {name, value} of arrays) map.get(name).value.push(...[value].flat());
console.log([...map.values()]);
Use lodash "uniqWith". As shown below
let _ = require("lodash");
var array = [
{ name: "foo1", value: "1" },
{ name: "foo1", value: "2" },
{ name: "foo2", value: "3" },
{ name: "foo1", value: "4" }
];
let merged = _.uniqWith(array, (pre, cur) => {
if (pre.name == cur.name) {
cur.value = cur.value + "," + pre.value;
return true;
}
return false;
});
console.log(merged);
// output: [{ name: "foo1", value: "1,2,4" }, { name: "foo2", value: "3" }];
Using reduce:
var mergedObj = array.reduce((acc, obj) => {
if (acc[obj.name]) {
acc[obj.name].value = acc[obj.name].value.isArray ?
acc[obj.name].value.concat(obj.value) :
[acc[obj.name].value].concat(obj.value);
} else {
acc[obj.name] = obj;
}
return acc;
}, {});
let output = [];
for (let prop in mergedObj) {
output.push(mergedObj[prop])
}
It's been a while since this question was asked, but I thought I'd chime in as well. For functions like this that execute a basic function you'll want to use over and over, I prefer to avoid longer-written functions and loops if I can help it and develop the function as a one-liner using shallow Array.prototype functions like .map() and some other ES6+ goodies like Object.entries() and Object.fromEntries(). Combining all these, we can execute a function like this relatively easily.
First, I take in however many objects you pass to the function as a rest parameter and prepend that with an empty object we'll use to collect all the keys and values.
[{}, ...objs]
Next, I use the .map() Array prototype function paired with Object.entries() to loop through all the entries of each object, and any sub-array elements each contains and then either set the empty object's key to that value if it has not yet been declared, or I push the new values to the object key if it has been declared.
[{},...objs].map((e,i,a) => i ? Object.entries(e).map(f => (a[0][f[0]] ? a[0][f[0]].push(...([f[1]].flat())) : (a[0][f[0]] = [f[1]].flat()))) : e)[0]
Finally, to replace any single-element-arrays with their contained value, I run another .map() function on the result array using both Object.entries() and Object.fromEntries(), similar to how we did before.
let getMergedObjs = (...objs) => Object.fromEntries(Object.entries([{},...objs].map((e,i,a) => i ? Object.entries(e).map(f => (a[0][f[0]] ? a[0][f[0]].push(...([f[1]].flat())) : (a[0][f[0]] = [f[1]].flat()))) : e)[0]).map(e => e.map((f,i) => i ? (f.length > 1 ? f : f[0]) : f)));
This will leave you with the final merged object, exactly as you prescribed it.
let a = {
a: [1,9],
b: 1,
c: 1
}
let b = {
a: 2,
b: 2
}
let c = {
b: 3,
c: 3,
d: 5
}
let getMergedObjs = (...objs) => Object.fromEntries(Object.entries([{},...objs].map((e,i,a) => i ? Object.entries(e).map(f => (a[0][f[0]] ? a[0][f[0]].push(...([f[1]].flat())) : (a[0][f[0]] = [f[1]].flat()))) : e)[0]).map(e => e.map((f,i) => i ? (f.length > 1 ? f : f[0]) : f)));
getMergedObjs(a,b,c); // { a: [ 1, 9, 2 ], b: [ 1, 2, 3 ], c: [ 1, 3 ], d: 5 }
Try this:
var array = [{name:"foo1",value:"val1"},{name:"foo1",value:["val2","val3"]},{name:"foo2",value:"val4"},{name:"foo2",value:"val5"}];
for(var j=0;j<array.length;j++){
var current = array[j];
for(var i=j+1;i<array.length;i++){
if(current.name = array[i].name){
if(!isArray(current.value))
current.value = [ current.value ];
if(isArray(array[i].value))
for(var v=0;v<array[i].value.length;v++)
current.value.push(array[i].value[v]);
else
current.value.push(array[i].value);
array.splice(i,1);
i++;
}
}
}
function isArray(myArray) {
return myArray.constructor.toString().indexOf("Array") > -1;
}
document.write(JSON.stringify(array));
This work too !
var array = [
{
name: "foo1",
value: "val1",
},
{
name: "foo1",
value: ["val2", "val3"],
},
{
name: "foo2",
value: "val4",
},
];
let arr2 = [];
array.forEach((element) => { // remove duplicate name
let match = arr2.find((r) => r.name == element.name);
if (match) {
} else {
arr2.push({ name: element.name, value: [] });
}
});
arr2.map((item) => {
array.map((e) => {
if (e.name == item.name) {
if (typeof e.value == "object") { //lets map if value is an object
e.value.map((z) => {
item.value.push(z);
});
} else {
item.value.push(e.value);
}
}
});
});
console.log(arr2);
const exampleObj = [{
year: 2016,
abd: 123
}, {
year: 2016,
abdc: 123
}, {
year: 2017,
abdcxc: 123
}, {
year: 2017,
abdcxcx: 123
}];
const listOfYears = [];
const finalObj = [];
exampleObj.map(sample => {
listOfYears.push(sample.year);
});
const uniqueList = [...new Set(listOfYears)];
uniqueList.map(list => {
finalObj.push({
year: list
});
});
exampleObj.map(sample => {
const sampleYear = sample.year;
finalObj.map((obj, index) => {
if (obj.year === sampleYear) {
finalObj[index] = Object.assign(sample, obj);
}
});
});
The final object be [{"year":2016,"abdc":123,"abd":123},{"year":2017,"abdcxcx":123,"abdcxc":123}]
const array = [{ name: "foo1", value: "val1" }, {name: "foo1", value: ["val2", "val3"] }, {name: "foo2", value: "val4"}];
const start = array.reduce((object, {name}) => ({...object, [name]: []}), {});
const result = array.reduce((object, {name, value}) => ({...object, [name]: [object[name], [value]].flat(2)}), start);
const output = Object.entries(result).map(([name, value]) => ({name: name, value: value}));
console.log(output);
try this :
var array = [
{
name: "foo1",
value: "val1"
}, {
name: "foo1",
value: [
"val2",
"val3"
]
}, {
name: "foo2",
value: "val4"
}
];
var output = [
{
name: "foo1",
value: [
"val1",
"val2",
"val3"
]
}, {
name: "foo2",
value: [
"val4"
]
}
];
bb = Object.assign( {}, array, output );
console.log(bb) ;
A much more easier approach is this 2022:
var array = [
{
name: "foo1",
value: "val1"
}, {
name: "foo1",
value: [
"val2",
"val3"
]
}, {
name: "foo2",
value: "val4"
}
];
var output = [
{
name: "foo1",
value: [
"val1",
"val2",
"val3"
]
},
{
name: "foo2",
value: [
"val4"
]
}
];
function mergeBasedOnKey(list){
let c = Object.values(list.reduce((a, b) => {
a[b.name] = a[b.name] || {name: b.name, value: []}
if(typeof(b['value']) == "string"){
a[b.name].value.push(b['value'])
}
else{
a[b.name].value = [...a[b.name].value, ...b.value]
}
return a
}, {}))
return c
}
let ans = mergeBasedOnKey(array)
console.log(ans)
I was looking for a quick, almost "one-liner" answer in this thread, provided that this is a trivial but common exercise.
I couldn't find any for my like. The other answers are fine but I am not much into boilerplate.
So, let me add one, then:
o = array.reduce((m,{name:n,value:v})=>({...m,[n]:[...m[n]||[],v].flat(1)}),{})
output = Object.entries(o).map(([n,v])=>({name:n,value:v}))
var array = [
{ name: "foo1", value: "val1"},
{ name: "foo1", value: ["val2","val3"] },
{ name: "foo2", value: "val4" }
]
o=array.reduce((m,{name:n,value:v})=>({...m,[n]:[...m[n]||[],v].flat(1)}),{})
output=Object.entries(o).map(([n,v])=>({name:n,value:v}))
console.log(output)