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I'm getting wrong output in Javascript Function?

I have function that looks through an array of objects (first argument) and returns an array of all objects that have matching name and value pairs (second argument). Each name and value pair of the source object has to be present in the object from the collection if it is to be included in the returned array.
function whatIsInAName(collection, source) {
let keyArr = Object.keys(source);
for (let i = 0; i < keyArr.length; i++) {
var arr = collection.filter(function(item) {
return item.hasOwnProperty(keyArr[i])
})
}
return arr.filter(function(item) {
for (let g = 0; g < keyArr.length; g++) {
return item[keyArr[g]] === source[keyArr[g]];
}
});
}
console.log(whatIsInAName([{
"a": 1,
"b": 2,
"c": 3
}], {
"a": 1,
"b": 9999,
"c": 3
}));
I should give an empty array [ ].
but It is giving [{"a": 1, "b": 2, "c": 3}]

You had an error in your second filter.
In for statement you were returning comparision result of first item from that statement and not checking if whole arr is equal.
In code below I have changed for statement to return false when items doesn't match. Then at the end there is returned true becouse there wasn't found any item that doesn't match with the other arr.
function whatIsInAName(collection, source) {
let keyArr = Object.keys(source);
for(let i = 0; i < keyArr.length; i++){
var arr = collection.filter(item => item.hasOwnProperty(keyArr[i]));
}
return arr.filter(item => {
for(let g = 0; g < keyArr.length; g++) {
if (item[keyArr[g]] !== source[keyArr[g]]) {
return false;
}
}
return true;
});
}
console.log(
whatIsInAName(
[{"a": 1, "b": 2, "c": 3}, {"a": 1, "b": 9999, "c": 3}],
{"a": 1, "b": 9999, "c": 3}
)
);

What is the first loop for? The arr created there is overwritten in every iteration of the loop. So the final arr will be the array of items which at least contain the last property in Object.keys(). You can apply your filter directly on the collections parameter.
function whatIsInAName(collection, source) {
let keys = Object.keys(source);
return collection.filter(item => keys.every(k => item[k] === source[k]));
}
console.log(whatIsInAName([
{"a": 1, "b": 9999, "c": 3 },
{"a": 2, "b": 9999, "c": 3 },
{"a": 1, "b": 2, "c": 3 },
{"a": 1, "b": 9999, "c": 3, "d": 4 }
],
{"a": 1, "b": 9999, "c": 3}));
Keep in mind that the equality check === will only work for primitive values but not for objects or arrays. Also this approach will accept additional properties in the items of the collection, that are not present in the source item.

How to group two arrays using key in node js

I have below two objects which I want to merge.
[
{
"response_code": 1,
"response_message": [{
"a": 1000,
"b": 1000001,
"c": 10000002
}]
}]
[
{
"response_code": 1,
"response_message": [{
"a": 2000,
"b": 2000001,
"c": 20000002
}]
}
]
I want to merge them like below by having only one value of response code and merge values of response message like below way.
{
"response_code": 1,
"response_message": [
{
"a": 1000,
"b": 1000001,
"c": 10000002
},
{
"a": 2000,
"b": 2000001,
"c": 20000002
}]
}
Really stuck with such complicated merging where I want only once the value of response code and merge the values of response message.
Here I want to remove response code value from other array and merge/group the response message value with fist array.

I whipped up a little function for you:
And in accordance with the concerns raised by you in the comments, along with the test case where response_message was a string, I have edited the code snippet to include multiple cases to test.
const inputs = [
[{
"response_code": 1,
"response_message": [{
"a": 1000,
"b": 1000001,
"c": 10000002
}]
},
{
"response_code": 1,
"response_message": [{
"p": 1000,
"q": 1000001,
"r": 10000002
}]
}
],
[{
"response_code": 1,
"response_message": [{
"a": 1000,
"b": 1000001,
"c": 10000002
}]
},
{
"response_code": 1,
"response_message": 'No data'
}
],
[{
"response_code": 1,
"response_message": 'No data'
},
{
"response_code": 1,
"response_message": 'No data'
}
]
]
const getGroupedArr = (arr) => {
const codeMap = arr.reduce((cMap,obj) => {
let existingMessageArr = cMap.get(obj.response_code);
let arrayToAdd = Array.isArray(obj.response_message) ? obj.response_message : [];
if(existingMessageArr){
existingMessageArr.push(...arrayToAdd);
} else {
cMap.set(obj.response_code,arrayToAdd);
}
return cMap;
},new Map());
const iterator = codeMap[Symbol.iterator]();
const resultArr = [];
for (let item of iterator) {
resultArr.push({
response_code: item[0],
response_message: item[1]
})
}
return resultArr;
}
inputs.forEach((inputArr,index) => {
console.log(`Result for input ${index+1}`,getGroupedArr(inputArr));
})
Notice that I used Map where in JS most people prefer objects because maps in JS are iterable, but with an object I would've had to do an extra Object.keys() step, so this makes is slightly more efficient than the object approach, though a little more verbose.
Also note that in the third case, when no object with a particular response_code has any data, the result would be an empty array rather than a string. In weakly typed environments like JS, it is always a good practice to maintain some type consistency (which actually makes the input value of 'No data' in response_code not ideal), otherwise you may need to put type checks everywhere (like in the edited funciton in the above snippet).
Same function can be used in a contraint you mentioned in the comments, when the objects with same response_code exist in two different arrays (the two input arrays can simply be merged into one):
const inputArr1 = [{
"response_code": 1,
"response_message": [{
"a": 1000,
"b": 1000001,
"c": 10000002
}]
}]
const inputArr2 = [{
"response_code": 1,
"response_message": [{
"p": 1000,
"q": 1000001,
"r": 10000002
}]
}]
const getGroupedArr = (arr) => {
const codeMap = arr.reduce((cMap,obj) => {
let existingMessageArr = cMap.get(obj.response_code);
let arrayToAdd = Array.isArray(obj.response_message) ? obj.response_message : [];
if(existingMessageArr){
existingMessageArr.push(...arrayToAdd);
} else {
cMap.set(obj.response_code,arrayToAdd);
}
return cMap;
},new Map());
const iterator = codeMap[Symbol.iterator]();
const resultArr = [];
for (let item of iterator) {
resultArr.push({
response_code: item[0],
response_message: item[1]
})
}
return resultArr;
}
console.log(getGroupedArr([...inputArr1,...inputArr2]));

I think you're looking for a groupby.
Check this good old post from stackoverflow and be aware of the different answers/ implementaions:
Most efficient method to groupby on an array of objects

const arrayOf0 = yourArray.filter(item => item.response_code===0)
const arrayOf1 = yourArray.filter(item => item.response_code===1)
const merged0 = {response_code: 0, response_message: []};
const merged1 = {response_code: 1, response_message: []};
arrayOf0.forEach(item => {
merged0.response_message.push(item.response_message[0]
})
arrayOf1.forEach(item => {
merged1.response_message.push(item.response_message[0]
})
Something like this?

I have resolved the array merging by below code.
const mergedArray = [];
myarray.forEach((obj, index) => {
var newObj = {}
if(index > 0){
if(mergedArray.length > 0){
for(let i=0; i<obj.response_message.length;i++){
mergedArray[0].response_message.push(obj.response_message[i]);
}
}
}else{
newObj["response_code"] = obj.response_code ;
newObj["response_message"] = obj.response_message;
mergedArray.push(newObj);
}
})

turn json obj to array

I have this array of objects
[{
"A": "thisA",
"B": "thisB",
"C": "thisC"
}, {
"A": "thatA",
"B": "thatB",
"C": "thatC"
}]
I'm trying to get this format as an end result: [["thisA","thisC"], ["thatA","thatC"]]
I'm trying with a for loop
var arr = [],
arr2 = [];
for (var = i; i < obj.length; i++) {
arr.push(obj[i].A, obj[i].C);
arr2.push(arr);
}
but I end up having ["thisA","thisC","thatA","thatC"]

You can do this with map() method.
const data = [{"A": "thisA","B": "thisB","C": "thisC"}, {"A": "thatA","B": "thatB","C": "thatC"}]
const result = data.map(({A, C}) => [A, C]);
console.log(result)

You coulöd push an array with the values. Beside that, you need to initialize i with zero.
var objects = [{ A: "thisA", B: "thisB", C: "thisC" }, { A: "thatA", B: "thatB", C: "thatC" }],
array = [],
i;
for (i = 0; i < objects.length; i++) {
array.push([objects[i].A, objects[i].C]);
}
console.log(array);

How to fill in missing keys in an Array of Objects?

I have an Array of Objects which should all have the same keys, but some of the keys are missing. I would like to fill in the missing keys with a generic value.
I am looking for a simple way to do that (natively or via a library), the code below I use now works, bit looks to my untrained eyes quite heavy and I am sure I reinvented the tedious way to do something while there is a simple one.
var arr = [{
"a": 1,
"b": 2,
"c": 3
},
{
"a": 10,
"c": 30
},
{
"b": 200,
"c": 300
},
]
// get the list of all keys
var allkeys = []
arr.forEach((objInArr) => {
allkeys = allkeys.concat(Object.keys(objInArr))
})
// check all arr entries for missing keys
arr.forEach((objInArr, i) => {
allkeys.forEach((key) => {
if (objInArr[key] === undefined) {
// the generic value, in this case 0
arr[i][key] = 0
}
})
})
console.log(arr)

Here is a version using property spread in object literals, although this will have very limited browser support:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator
var arr = [{
"a": 1,
"b": 2,
"c": 3
},
{
"a": 10,
"c": 30
},
{
"b": 200,
"c": 300
},
]
// Create an object with all the keys in it
// This will return one object containing all keys the items
let obj = arr.reduce((res, item) => ({...res, ...item}));
// Get those keys as an array
let keys = Object.keys(obj);
// Create an object with all keys set to the default value (0)
let def = keys.reduce((result, key) => {
result[key] = 0
return result;
}, {});
// Use object destrucuring to replace all default values with the ones we have
let result = arr.map((item) => ({...def, ...item}));
// Log result
console.log(result);

Your version is fine, although I would probably avoid all those array concat calls by just building up an object (or Set) with the keys. It's also a bit less clunky with for-of:
var arr = [{
"a": 1,
"b": 2,
"c": 3
},
{
"a": 10,
"c": 30
},
{
"b": 200,
"c": 300
},
];
// Get all the keys
const keyObj = Object.create(null);
for (const entry of arr) {
for (const key of Object.keys(entry)) {
keyObj[key] = true;
}
}
const allkeys = Object.keys(keyObj);
// Check all arr entries for missing keys
for (const entry of arr) {
for (const key of allkeys) {
if (entry[key] === undefined) { // ***I'd change this
entry[key] = 0;
}
}
}
console.log(arr);
.as-console-wrapper {
max-height: 100% !important;
}
Re *** I'd change this: Note that there's a difference between a property that exists and has the value undefined and a property that doesn't exist at all. Your code is treating them as the same thing. Of course, if you know they won't have the value undefined (for instance, because of the API you're getting them from)...

You can use Object.assign to merge each element with an object holding default key-values:
var arr = [{
"a": 1,
"b": 2,
"c": 3
},
{
"a": 10,
"c": 30
},
{
"b": 200,
"c": 300
},
];
var defaultObj = arr.reduce((m, o) => (Object.keys(o).forEach(key => m[key] = 0), m), {});
arr = arr.map(e => Object.assign({}, defaultObj, e));
console.log(arr);

Merge JS objects without overwriting

Suppose you have two objects:
var foo = {
a : 1,
b : 2
};
var bar = {
a : 3,
b : 4
}
What's the best way to merge them (and allow deep merging) to create this:
var foobar = {
a : [1, 3],
b : [2, 4]
}
Edit for question clarification: Ideally, in the case of an existing property in one and not the other, I would expect an array to still be created, for normalization purposes and to allow for further reduction of the map, however the answers I'm seeing below are more than sufficient. For the purposes of this exercise, I was only looking for string or numerical merges, so I hadn't entertained every possible situational case. If you held a gun to my head and asked me to make a choice, though, I'd say default to arrays.
Thanks all for your contributions.

This ought to do what you're looking for. It will recursively merge arbitrarily deep objects into arrays.
// deepmerge by Zachary Murray (dremelofdeath) CC-BY-SA 3.0
function deepmerge(foo, bar) {
var merged = {};
for (var each in bar) {
if (foo.hasOwnProperty(each) && bar.hasOwnProperty(each)) {
if (typeof(foo[each]) == "object" && typeof(bar[each]) == "object") {
merged[each] = deepmerge(foo[each], bar[each]);
} else {
merged[each] = [foo[each], bar[each]];
}
} else if(bar.hasOwnProperty(each)) {
merged[each] = bar[each];
}
}
for (var each in foo) {
if (!(each in bar) && foo.hasOwnProperty(each)) {
merged[each] = foo[each];
}
}
return merged;
}
And this one will do the same, except that the merged object will include copies of inherited properties. This probably isn't what you're looking for (as per RobG's comments below), but if that is actually what you are looking for, then here it is:
// deepmerge_inh by Zachary Murray (dremelofdeath) CC-BY-SA 3.0
function deepmerge_inh(foo, bar) {
var merged = {};
for (var each in bar) {
if (each in foo) {
if (typeof(foo[each]) == "object" && typeof(bar[each]) == "object") {
merged[each] = deepmerge(foo[each], bar[each]);
} else {
merged[each] = [foo[each], bar[each]];
}
} else {
merged[each] = bar[each];
}
}
for (var each in foo) {
if (!(each in bar)) {
merged[each] = foo[each];
}
}
return merged;
}
I tried it out with your example on http://jsconsole.com, and it worked fine:
deepmerge(foo, bar)
{"a": [1, 3], "b": [2, 4]}
bar
{"a": 3, "b": 4}
foo
{"a": 1, "b": 2}
Slightly more complicated objects worked as well:
deepmerge(as, po)
{"a": ["asdf", "poui"], "b": 4, "c": {"q": [1, 444], "w": [function () {return 5;}, function () {return 1123;}]}, "o": {"b": {"t": "cats"}, "q": 7}, "p": 764}
po
{"a": "poui", "c": {"q": 444, "w": function () {return 1123;}}, "o": {"b": {"t": "cats"}, "q": 7}, "p": 764}
as
{"a": "asdf", "b": 4, "c": {"q": 1, "w": function () {return 5;}}}

Presumably you would iterate over one object and copy its property names to a new object and values to arrays assigned to those properties. Iterate over subsequent objects, adding properties and arrays if they don't already exist or adding their values to existing properties and arrays.
e.g.
function mergeObjects(a, b, c) {
c = c || {};
var p;
for (p in a) {
if (a.hasOwnProperty(p)) {
if (c.hasOwnProperty(p)) {
c[p].push(a[p]);
} else {
c[p] = [a[p]];
}
}
}
for (p in b) {
if (b.hasOwnProperty(p)) {
if (c.hasOwnProperty(p)) {
c[p].push(b[p]);
} else {
c[p] = [b[p]];
}
}
}
return c;
}
You could modify it to handle any number of objects by iterating over the arguments supplied, but that would make passing the object to merge into more difficult.

https://lodash.com/docs/3.10.1#merge
// using a customizer callback
var object = {
'fruits': ['apple'],
'vegetables': ['beet']
};
var other = {
'fruits': ['banana'],
'vegetables': ['carrot']
};
_.merge(object, other, function(a, b) {
if (_.isArray(a)) {
return a.concat(b);
}
});
// → { 'fruits': ['apple', 'banana'], 'vegetables': ['beet', 'carrot'] }

I just leave it here.
Shallow merging with values as arrays.
const foo = {a: 1, b: 2}
const bar = {a: 2, с: 4}
const baz = {a: 3, b: 3}
const myMerge = (...args) => args
.flatMap(Object.entries)
.reduce((acc, [key, value]) => {
acc[key] ??= []
acc[key].push(value)
return acc
}, {})
console.log(myMerge(foo, bar, baz))
//{ a: [1, 2, 3],
// b: [2, 3],
// с: [4] }
.as-console-wrapper { max-height: 100% !important; top: 0 }