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JS -Append key to matching array, object values

I would like to push key values to objects in array1 from other objects of array2
To do so it needs to search a corresponding values in both arrays, then push the right key.
let array1 = [
{
"Ref": "28189-060-B",
"Otherkey": "Whatever"
},
{
"Ref": "18182-250-B",
"Otherkey": "Whatever2"
},
{
"Ref": "55187-753-B",
"Otherkey": "Whatever3"
}
]
let array2 = [
{
"Ref": "28189-060-ABCD",
"Style": "Red"
},
{
"Ref": "18182-250-ABCD",
"Style": "Blue"
},
{
"Ref": "55187-753-ABCD",
"Style": "Yellow"
}
]
The function need to loop through all objects in array1, look at the first 9 characters of Ref values, find a match in array2 Ref (only first 9 characters are identical). When there is a match push the "Style" from array2 into the corresponding object in array1
I tried with Object.key.foreach(), map(), with substr to get only 9 characters, with find()... all of this has been a big mess and not working...
Expected result :
let array1 = [
{
"Ref": "18182-250-B",
"Otherkey": "Whatever2",
"Style": "Blue"
},
{
"Ref": "28189-060-B",
"Otherkey": "Whatever",
"Style": "Red"
},
{
"Ref": "55187-753-B",
"Otherkey": "Whatever3",
"Style": "Yellow"
}
]

Assuming those properties are all meant to be Ref (some are Global_Style), you can use forEach and find:
let array1 = [{"Ref":"28189-060-B","Otherkey":"Whatever"},{"Ref":"18182-250-B","Otherkey":"Whatever2"},{"Ref":"55187-753-B","Otherkey":"Whatever3"}];
let array2 = [{"Ref":"28189-060-ABCD","Style":"Red"},{"Ref":"18182-250-ABCD","Style":"Blue"},{"Ref":"55187-753-ABCD","Style":"Yellow"}];
const shorterRef = (ref) => ref.substr(0, 9);
array1.forEach(obj => {
const a1Ref = shorterRef(obj.Ref);
const arr2Obj = array2.find(tmp => shorterRef(tmp.Ref) === a1Ref);
if (arr2Obj) obj.Style = arr2Obj.Style;
});
console.log(array1);
If you didn't want to mutate the array go with map:
let array1 = [{"Ref":"28189-060-B","Otherkey":"Whatever"},{"Ref":"18182-250-B","Otherkey":"Whatever2"},{"Ref":"55187-753-B","Otherkey":"Whatever3"}];
let array2 = [{"Ref":"28189-060-ABCD","Style":"Red"},{"Ref":"18182-250-ABCD","Style":"Blue"},{"Ref":"55187-753-ABCD","Style":"Yellow"}];
const shorterRef = (ref) => ref.substr(0, 9);
const out = array1.map(obj => {
const a1Ref = shorterRef(obj.Ref);
const arr2Obj = array2.find(tmp => shorterRef(tmp.Ref) === a1Ref);
if (arr2Obj) return { ...obj, Style: arr2Obj.Style };
});
console.log(out);

var arrMap = {};
array1.forEach(function(x){
if(!arrMap[x.Ref.substring(0,9)]){
arrMap[x.Ref.substring(0,9)] = x;
}
});
array2.forEach(function(x){
if(Object.keys(arrMap).includes(x.Ref.substring(0,9))){
arrMap[x.Ref.substring(0,9)] = Object.assign(arrMap[x.Ref.substring(0,9)], {"Style": x.Style});
}
});
console.log(Object.values(arrMap));

Something like this may be what you want:
array1.forEach(function (element1) {
array2.forEach(function (element2){
addStyle(element1, element2);
});
});
function addStyle(obj1, obj2){
if (obj1.Ref && obj2.Ref){
let Ref1 = obj1.Ref.substr(0,8);
let Ref2 = obj2.Ref.substr(0, 8);
if (Ref1 === Ref2){
obj1.Style = obj2.Style;
};
}
}
So we loop through the fist array and for each item we loop through the second array.
Then we check if the expected fields are present and if so we compare them. If they match we add the "Style" field and move to the next object

The Below code will work although we might be able to optimize it further.
var newArr = []
for(let k in array1){
for(let i in array2){
console.log(array2[i]['Ref'].substr(0,9))
if(array1[k]['Ref'].substr(0,9) == array2[i]['Ref'].substr(0,9)){
let temp = array1[k]
temp['Style'] = array2[i]['Style']
newArr.push(temp)
}
}
}

The first solution is a bit complex.
You probable have a typo in array1 as your first key is not consistent. instead of Global_Stylecode you probably meant Ref, Anyway most likely it should have the same key. If we assume that the key is Ref, then
array1.forEach( ({Ref: Ref1, Otherkey}, index) => {
const Ref1Sub = Ref1.substring(0, 9);
array2.forEach(({Ref: Ref2, Style}) => {
if (Ref2.includes(Ref1Sub)) {
array1[index].Style = Style;
}
})
});
Also there is no need to define arrays as let. const will be fine.

How to merge an array of objects by key?

I have this object:
[{
"NOMOR_CB": "CB/20-0718",
"ITEM": "ABC"
}, {
"NOMOR_CB": "CB/20-0719",
"ITEM": "A1"
}, {
"NOMOR_CB": "CB/20-0719",
"ITEM": "A2"
}]
I'd to merge the values of the same NOMOR_CB so the values of the same NOMOR_CB is combined. This is the desired output.
[{
"NOMOR_CB": "CB/20-0718",
"ITEM": "ABC"
}, {
"NOMOR_CB": "CB/20-0719",
"ITEM": "A1, A2"
}]
How do I loop over the object to have the desired output?
My current loop (unable to combine the values):
var arr_test = "[";
$.each(response.arr_json, function(i, data) {
arr_test += '{"NOMOR_CB":"'+ data.NOMOR_CB +'",';
arr_test += '"ITEM":"'+ data.ITEM +'"},';
})
var test = arr_test.replace(/,\s*$/, "");
test += "]";
document.write(test);

You can use .reduce() to summarise your array into an object. Use Object.entries to convert the object into an array. You can map to form the desired object format.
let arr = [{"NOMOR_CB":"CB/20-0718","ITEM":"ABC"},{"NOMOR_CB":"CB/20-0719","ITEM":"A1"},{"NOMOR_CB":"CB/20-0719","ITEM":"A2"}];
let result = Object.entries(arr.reduce((c, {NOMOR_CB,ITEM}) => {
c[NOMOR_CB] = c[NOMOR_CB] || [];
c[NOMOR_CB].push(ITEM);
return c;
}, {})).map(([i, a]) => Object.assign({}, {NOMOR_CB: i,ITEM: a.join(', ')}));
let str = JSON.stringify(result); //Optional. Based on your code, you are trying to make a string.
console.log(str);
And dont concatenate strings to form a json. You can use JSON.stringify(result); to convert js object to string.
Doc: .reduce(), .map()

formatting dynamic json array

I have an json array as follows:
Maindata=[
{"name":"string1"},
{"name":"string2"},
{"name":"string3"}
];
what I need is an array of following type:
data=[
{
"name":"string1",
"name":"string2",
"name":"string3"
}
];
can anybody help me with some methods to obtain required json from original array.
(note: maindata is json array formed dynamically thats why its structure is like that)
Thanks in advance

You could use Object.assign and spread the array elements.
var array = [{ name1: "string1" }, { name2: "string2" }, { name3: "string3" }],
object = Object.assign({}, ...array);
console.log(object);

With reduce, you can do like following
var Maindata = [{
"name1": "string"
}, {
"name2": "string"
}, {
"name3": "string"
}];
var finalObj = Maindata.reduce((acc, cur) => {
Object.assign(acc, cur);
return acc;
}, {})
console.log(finalObj);

You can use Array.forEach or Array.reduce to iterate though the items of the Maindata object and for each item you can iterate through its keys(using Object.keys) and group the data into a new structure.(See the below snippet)
Solution using Array.forEach
var Maindata=[
{"name1":"string1"},
{"name2":"string2"},
{"name3":"string3"}
];
var result = {};
var newMaindata=[];
Maindata.forEach(function(el){
Object.keys(el).forEach(function(key){
result[key]=el[key];
});
});
newMaindata.push(result);
console.log(newMaindata);
Solution using Array.reduce
var Maindata = [{
"name1": "string1"
}, {
"name2": "string2"
}, {
"name3": "string3"
}];
var result ;
var newMaindata = [];
result = Maindata.reduce(function(acc,el) {
Object.keys(el).forEach(function(key) {
acc[key] = el[key];
});
return acc;
},{});
newMaindata.push(result);
console.log(newMaindata);

array map, map array as a key of an array

I know the title might sounds confusing, but i'm stuck for an hour using $.each. Basically I have 2 arrays
[{"section_name":"abc","id":1},{"section_name":"xyz","id":2}];
and [{"toy":"car","section_id":1},{"tool":"knife","section_id":1},{"weapons":"cutter","section_id":2}];
How do I put one into another as a new property key like
[{
"section_name": "abc",
"id": 1,
"new_property_name": [{
"toy": "car"
}, {
"tool": "knife"
}]
}, {
"section_name": "xyz",
"id": 2,
"new_property_name": [{
"weapon": "cutter"
}]
}]

ES6 Solution :
const arr = [{"section_name":"abc","id":1},{"section_name":"xyz","id":2}];
const arr2 = [{"toy":"car","id":1},{"tool":"knife","id":1},{"weapons":"cutter","id":2}];
const res = arr.map((section,index) => {
section.new_property_name = arr2.filter(item => item.id === section.id);
return section;
});
EDIT : Like georg mentionned in the comments, the solution above is actually mutating arr, it modifies the original arr (if you log the arr after mapping it, you will see it has changed, mutated the arr and have the new_property_name). It makes the .map() useless, a simple forEach() is indeed more appropriate and save one line.
arr.forEach(section => {
section.new_property_name = arr2.filter(item => item.id === section.id));
});

try this
var data1 = [{"section_name":"abc","id":1},{"section_name":"xyz","id":2}];
var data2 = [{"toy":"car","id":1},{"tool":"knife","id":1},{"weapons":"cutter","id":2}];
var map = {};
//first iterate data1 the create a map of all the objects by its ids
data1.forEach( function( obj ){ map[ obj.id ] = obj });
//Iterate data2 and populate the new_property_name of all the ids
data2.forEach( function(obj){
var id = obj.id;
map[ id ].new_property_name = map[ id ].new_property_name || [];
delete obj.id;
map[ id ].new_property_name.push( obj );
});
//just get only the values from the map
var output = Object.keys(map).map(function(key){ return map[ key ] });
console.log(output);

You could use ah hash table for look up and build a new object for inserting into the new_property_name array.
var array1 = [{ "section_name": "abc", "id": 1 }, { "section_name": "xyz", "id": 2 }],
array2 = [{ "toy": "car", "section_id": 1 }, { "tool": "knife", "section_id": 1 }, { "weapons": "cutter", "section_id": 2 }],
hash = Object.create(null);
array1.forEach(function (a) {
a.new_property_name = [];
hash[a.id] = a;
});
array2.forEach(function (a) {
hash[a.section_id].new_property_name.push(Object.keys(a).reduce(function (r, k) {
if (k !== 'section_id') {
r[k] = a[k];
}
return r;
}, {}));
});
console.log(array1);

Seems like by using Jquery $.merge() Function you can achieve what you need. Then we have concat function too which can be used to merge one array with another.

Use Object.assign()
In your case you can do it like Object.assign(array1[0], array2[0]).
It's very good for combining objects, so in your case you just need to combine your objects within the array.
Example of code:
var objA = [{"section_name":"abc","id":1},{"section_name":"xyz","id":2}];
var objB = [{"toy":"car","section_id":1},{"tool":"knife","section_id":1},{"weapons":"cutter","section_id":2}];
var objC = Object.assign({},objA[0],objB[0]);
console.log(JSON.stringify(objC));// {"section_name":"abc","id":1,"toy":"car","section_id":1}
For more info, you can refer here: Object.assign()

var firstArray = [{"section_name":"abc","id":1},{"section_name":"xyz","id":2}],
secondArray = [{"toy":"car","section_id":1},{"tool":"knife","section_id":1},{"weapons":"cutter","section_id":2}];
var hash = Object.create(null);
firstArray.forEach(s => {
hash[s.id] = s;
s['new_property_name'] = [];
});
secondArray.forEach(i => hash[i['section_id']]['new_property_name'].push(i));
console.log(firstArray);

Finding an array's objects that are not present in another array by property

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));