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Indent object values in an array of nested objects in JavaScript

I have an array like this :
[
{
name: 'foo',
nestedArray: [
{
name: 'bar',
nestedArray: []
}
]
}
]
What's the best way to have a flatten array that looks like this ?
[
{
name: 'foo',
nestedArray: [
{
name: 'bar',
nestedArray: []
}
]
},
{
name: ' bar',
nestedArray: []
}
]

You can try by iterating input array and moving out nested array objects into outer one. I hope this will work as per your expectation :
// Input array
const inputArray = [
{
name: 'foo',
nestedArray: [
{
name: 'bar',
nestedArray: []
}
]
}
];
// Result array
const res = [];
// Iterating input array and moving out nested array objects into outer one.
inputArray.forEach((obj) => {
res.push(obj);
obj.nestedArray.forEach((nestedObj) => {
res.push(nestedObj);
});
});
// Assigning result
console.log(res);

Get count from Array of arrays

I have an array of arrays below. With ES6, how can I get a count of each value Good, Excellent & Wow into a new array e.g [{name: Good, count: 4} {name: Excellent, count: 5}, {name:Wow, count:2}] in dynamic style. I am attempting to use Object.assign but I am failing to "unique" out the count of the key plus instead, I need to use an array as I am trying to render this out on the front end. Do I need to use reduce? how?
let k = 0
const stats = {}
const remarks = [
[{name: "Good"}],
[{name: "Good"}, {name: "Excellent"}],
[{name: "Good"}, {name: "Excellent"}, {name: "Wow"}],
[{name: "Good"}, {name: "Excellent"}, {name: "Wow"}],
[{name: "Excellent"}],
[{name: "Excellent"}]
]
remarks.forEach((arr) => {
arr.map((e) => {
Object.assign(stats, { [e.name]: k = k + 1 })
})
})
console.log(stats);
Output:
stats: {Good: 8, Excellent: 11, Wow: 9}
Which is Incorrect plus I need to use an array.
Expected output:
[{name: Good, count: 4} {name: Excellent, count: 5}, {name:Wow, count:2}]

Flatten the array of arrays and reduce it starting with an object like : { Good: 0, Excellent: 0, Wow: 0}
then .map the Object.entries of the result to transform it to an array :
const remarks = [
[{ name: "Good" }],
[{ name: "Good" }, { name: "Excellent" }],
[{ name: "Good" }, { name: "Excellent" }, { name: "Wow" }],
[{ name: "Good" }, { name: "Excellent" }, { name: "Wow" }],
[{ name: "Excellent" }],
[{ name: "Excellent" }]
];
const result = Object.entries(
remarks.flat().reduce(
(all, { name }) => {
all[name] += 1;
return all;
},
{ Good: 0, Excellent: 0, Wow: 0 }
)
).map(([name, count]) => ({ name, count }));
console.log(result);

You can try below logic:
var data = [[{name: "Good"}],[{name: "Good"}, {name:"Excellent"}],[{name: "Good"}, {name:"Excellent"}, {name:"Wow"}],[{name: "Good"}, {name:"Excellent"}, {name:"Wow"}],[{name:"Excellent"}],[{name:"Excellent"}]]
var nData = [];
(data || []).forEach( e => {
(e || []).forEach(ei => {
var i = (index = nData.findIndex(d => d.name === ei.name)) >=0 ? index : nData.length;
nData[i] = {
name: ei.name,
count : (nData[i] && nData[i].count ? nData[i].count : 0)+1
}
});
});
console.log(nData);
Hope this helps!

You can use reduce, then convert the result into an array of objects:
const counts = remarks.reduce((result, list) => {
list.forEach(remark => {
result[remark.name] = (result[remark.name] || 0) + 1;
});
}, {});
const finalResult = [];
for (let name in counts) {
finalResult.push({name, count: counts[name]});
}

You could achieve this pretty easily by:
1) Flattening the nested array into 1 single level array.
2) Iterating over the flat array and create a "count map" by using Array.prototype.reduce
For example:
const remarks = [
[{
name: 'Good'
}],
[{
name: 'Good'
}, {
name: 'Excellent'
}],
[{
name: 'Good'
}, {
name: 'Excellent'
}, {
name: 'Wow'
}],
[{
name: 'Good'
}, {
name: 'Excellent'
}, {
name: 'Wow'
}],
[{
name: 'Excellent'
}],
[{
name: 'Excellent'
}]
]
const flatten = arr => arr.reduce((accum, el) => accum.concat(el), [])
const map = flatten(remarks).reduce((accum, el) => {
if (accum[el.name]) {
accum[el.name] += 1;
} else {
accum[el.name] = 1;
}
return accum;
}, {});
console.log(map)

First find the counts using reduce than pass that to another function to get the desired view structure:
const Good = 1,
Excellent = 2,
Wow = 3;
const remarks = [
[{name: Good}],
[{name: Good}, {name:Excellent}],
[{name: Good}, {name:Excellent}, {name:Wow}],
[{name: Good}, {name:Excellent}, {name:Wow}],
[{name:Excellent}],
[{name:Excellent}]
];
/*
[{name: Good, count: 4} {name: Excellent, count: 5}, {name:Wow, count:2}]
*/
function counts(remarks) {
return remarks.flat().reduce((acc, v) => {
const name = v.name;
let count = acc[name] || 0;
return {
...acc,
[name]: count + 1
}
}, {});
}
function view(counts) {
return Object.keys(counts).map(key => {
let count = counts[key];
return { name: key, count };
})
}
console.log(view(counts(remarks)));

Any time you are making a smaller set of data, or transforming data, in JavaScript reduce should be the first method you attempt to use. In this case, you may want to pair it with an indexer (hence preloading with an array of index and an array of result).
This works in one pass without needing to know the name values up front.
const remarks = [
[{name: "Good"}],
[{name: "Good"}, {name: "Excellent"}],
[{name: "Good"}, {name: "Excellent"}, {name: "Wow"}],
[{name: "Good"}, {name: "Excellent"}, {name: "Wow"}],
[{name: "Excellent"}],
[{name: "Excellent"}]
];
const stats = remarks.reduce((p,c) => (
c.forEach( ({name}) => {
if(!p[0].hasOwnProperty(name)){
p[1].push({name:name,count:0});
p[0][name] = p[1].length - 1;
}
p[1][p[0][name]].count++;
}),p),[{},[]])[1];
console.log(stats);

A slightly more concise and definitely less readable approach (but it's worth to mention) could be:
const remarks = [
[{ name: "Good" }],
[{ name: "Good" }, { name: "Excellent" }],
[{ name: "Good" }, { name: "Excellent" }, { name: "Wow" }],
[{ name: "Good" }, { name: "Excellent" }, { name: "Wow" }],
[{ name: "Excellent" }],
[{ name: "Excellent" }]
];
const stats = Object.entries(
remarks
.flat()
.reduce((acc, {name}) => (acc[name] = -~acc[name], acc), {})))
).map(([name, count]) => ({ name, count }));
console.log(stats);
It uses the comma operator in the reducer to returns the accumulator; and the bitwise operator NOT to create a counter without the needs to initialize the object upfront with all the names.

const flattenedRemarks = _.flatten(remarks);
const groupedRemarks = _.groupBy(flattenedRemarks, (remark) => remark.name);
const remarkCounts = _.mapValues(groupedRemarks, (group) => group.length);

const data = {
"mchale": {
"classes":["ESJ030", "SCI339"], // get the length
"faculty":["Hardy", "Vikrum"] // get the length
},
"lawerence":{
"classes":["ENG001"], // get the length
"faculty":["Speedman", "Lee", "Lazenhower"] // get the length
}
};
const count = Object.keys(data).map(campusName => {
const campus = data[campusName];
return Object.keys(campus).map(key => campus[key].length).reduce((p, c) => p + c, 0);
}).reduce((p, c) => p + c, 0);
console.log(count);

How to check if all objects of array are included another array?

I am trying to check if object array A includes objects from B.
let A = [
{ name: "Max" },
{ name: "Jhon" },
{ name: "Naton" },
]
let B = [
{ name: "Max" },
{ name: "Naton" },
]
So B has two objects that is in array A. How to check this ?
I am trying to achieve it with includes :
for(let entry of this.b){
if(this.a.includes(entry)){
console.log('includes');
}
}
But I get false on includes.

The method Array.includes() compare the entries of the array with the given value. Because your array entries are objects, it will not match. You have to loop at the array yourself and make the comparison.
Array.some() loops on an array and returns true if you returns true at least one. This method is useful when you want to verify something. In our example, we want to verify if the array a contains the b entry.
const a = [{
name: 'Max',
},
{
name: 'Jhon',
},
{
name: 'Naton',
},
];
const b = [{
name: 'Max',
},
{
name: 'Naton',
},
{
name: 'Daddy',
},
];
console.log(b.map(x => a.some(y => y.name === x.name)));
If I break it down :
const a = [{
name: 'Max',
},
{
name: 'Jhon',
},
{
name: 'Naton',
},
];
const b = [{
name: 'Max',
},
{
name: 'Naton',
},
{
name: 'Daddy',
},
];
// Loop on every entry of the b array
b.forEach((x) => {
// x here represent one entry
// first it will worth { name: 'Max' }, then { name: 'Naton' } ...
// for each value we are going to look at a if we can find a match
const isThereAMatch = a.some((y) => {
// y here is worth one entry of the a array
if (y.name === x.name) return true;
return false;
});
if (isThereAMatch === true) {
console.log(`We have found ${x.name} in a`);
} else {
console.log(`We have not found ${x.name} in a`);
}
});

You have to use another loop, then check the property name:
var a = [
{name: "Max"},
{name: "Jhon"},
{name: "Naton"},
];
var b = [
{name: "Max"},
{name: "Naton"},
];
for(let entry of b){
for(let entry2 of a){
if(entry2.name == entry.name){
console.log('includes', entry.name);
}
}
}
OR: You can use string version of object to check with includes():
var a = [
{name: "Max"},
{name: "Jhon"},
{name: "Naton"},
];
var b = [
{name: "Max"},
{name: "Naton"},
];
var aTemp = a.map(i => JSON.stringify(i));
var bTemp = b.map(i => JSON.stringify(i));
for(let entry of bTemp){
if(aTemp.includes(entry)){
console.log('includes', entry);
}
}

When you use Array#includes() method it will always return false because it's comparing objects which aren't equal because they aren't referencing the same object.
You should compare objects properties and not whole objects, you can do it using Array#some() method like this:
for (let entry of this.b) {
if (this.b.some(x => x.name === entry.name)) {
console.log('includes');
}
}
Demo:
A = [{
name: "Max"
},
{
name: "Jhon"
},
{
name: "Naton"
},
]
B = [{
name: "Max"
},
{
name: "Naton"
},
]
//Filter objects that exists in both arrays
let result = A.filter(el=> B.some(x => x.name === el.name));
console.log(result);

Override all keys of an object but its id

I have a similar object as this one but it has quite more keys. I want to update all of its keys but id. I can do so manually. But I think it is not the best way.
const o = {
name: "unknow",
key: "key"
value: "value"
id ": 12
}
How can I update/override all keys of an object but id?
Update
The two object has the same keys. But their keys have different value. I need to update all keys of the first object excluding its id.

I suspect that you're looking for something like assignBut: it sets properties of ob on oa but the specified one:
const assignBut = (prop, oa, ob) => {
for (let key of Object.keys(ob))
// Check that I also verify that the property
// to set should be part of "oa" object. This
// prevents adding new properties: it just updates
// existing ones.
if (key !== prop && oa.hasOwnProperty(key))
oa[key] = ob[key]
}
const oa = {
name: "unknow",
key: "key",
value: "value",
id: 12
}
const ob = {
name: "xxx",
key: "yyy",
value: "zzz",
other: "aaa",
yetAnother: 289,
id: 15
}
assignBut('id', oa, ob)
console.log(oa)
Another approach to omit a given property
One may take advantage of destructuring and computed property names to omit the whole given property so the for..of just needs to check that each property from ob is present in oa to set it.
Also, one may save the check to verify that a property from ob exists in oa performing an intersection of oa and ob keys:
const oa = {
name: "unknow",
key: "key",
value: "value",
id: 12
}
const ob = {
name: "xxx",
key: "yyy",
value: "zzz",
other: "aaa",
yetAnother: 289,
id: 15
}
const intersect = (xs, ys) => xs.filter(x => ys.includes(x))
const assignBut = (prop, oa, {
[prop]: omitted,
...ob
}) => {
const sharedKeys = intersect(Object.keys(oa), Object.keys(ob))
for (let key of sharedKeys)
oa[key] = ob[key]
}
assignBut('id', oa, ob)
console.log(oa)

You can iterate through Object.keys like below -
const o = {
name: "unknow",
key: "key",
value: "value",
id : 12
};
Object.keys(o).forEach((key)=>{
if(key !=="id"){
console.log(o[key]) //value
}
}
);

Following approach is based on lodash. If you are not comfortable using a library, please ignore.
Benefit of omit is that you can pass an array of keys and ignore multiple keys.
There is also a function called pick where you can only pick certain properties you need.
_.omit
const o = { name: "unknow", key: "key", value: "value", id: 12 }
const props = { name: "foo", key: "key2", value: "bar", id: 15 };
const final = _.assign({}, o, _.omit(props, 'id'));
console.log(final)
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>
_.pick
const o = { name: "unknow", key: "key", value: "value", id: 12 }
const props = { name: "foo", key: "key2", value: "bar", id: 15, test: 'abc', hello: 'world' };
const final = _.assign({}, o, _.pick(props, ['name', 'key', 'value']));
console.log(final)
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>
pure js implementation
const o = { name: "unknow", key: "key", value: "value", id: 12 }
const propsOmit = { name: "foo", key: "key2", value: "bar", id: 15 };
const propsPick = { name: "foo", key: "key2", value: "bar", id: 15, test: 'abc', hello: 'world' };
const finalOmit = Object.assign({}, o, omit(propsOmit, 'id'));
const finalPick = Object.assign({}, o, omit(propsPick, ['id', 'test', 'hello']));
console.log(finalOmit)
console.log(finalPick)
function omit(obj, ignoreKeys) {
if (!Array.isArray(ignoreKeys)) {
ignoreKeys = [ ignoreKeys ];
}
const copy = Object.assign({}, obj);
ignoreKeys.forEach((k) => delete copy[k]);
return copy;
}
function pick(obj, selectKeys) {
if (!Array.isArray(selectKeys)) {
selectKeys = [ selectKeys ];
}
const copy = {};
ignoreKeys.forEach((k) => copy[k] = obj[k]);
return copy;
}
References:
_.assign
_.omit
_.pick

Best way to compare an array of strings to an array objects with string properties?

I have an array of object, within those objects is a name property.
const objArr = [ { name: "Avram" }, { name: "Andy" } ];
I’m collecting an array of strings from an outside source containing names.
const strArr = [ "Avram", "Andy", "Brandon" ];
If strArr contains a string that does not exist as a property name on an object in objArr, I need to create a new object and push it to objArr.
For example: objArr.push( { name: "Brandon" } );
Obviously, I can use nested loops, but I’d like to avoid that if possible. What is the best way to do this programmatically?

like this
const objArr = [ { name: "Avram" }, { name: "Andy" } ];
const strArr = [ "Avram", "Andy", "Brandon" ];
const names= objArr.map(x => x.name);
strArr.forEach(str => {
if (! names.includes(str) ) {
objArr.push({name: str});
}
});
console.log(objArr);

function fillMissing(arr, names) {
names.forEach(name => { // for each name in names
if(arr.every(obj => obj.name !== name)) { // if every object obj in the array arr has a name diferent than this name (this name doesn't exist in arr)
arr.push({name}); // then add an object with that name to arr
}
});
}
const objArr = [ { name: "Avram" }, { name: "Andy" } ];
const strArr = [ "Avram", "Andy", "Brandon" ];
fillMissing(objArr, strArr);
console.log(objArr);

Map objArr to same structure as strArr. Then concat the 2 arrays. Run it through a Set to remove duplicates, then remap to correct array of object
const objArr = [ { name: "Avram" }, { name: "Andy" }, { name: "John"} ];
const strArr = [ "Avram", "Andy", "Brandon" ];
const res = Array.from(new Set(objArr.map(i=>i.name).concat(strArr))).map(i=>({name:i}))
console.log(res);

const objArr = [ { name: "Avram" }, { name: "Andy" } ];
const strArr = [ "Avram", "Andy", "Brandon" ];
const objNamesArr = objArr.map((obj) => obj.name)
strArr.forEach((ele) => objNamesArr.indexOf(ele) == -1 && objArr.push({name:ele}))
console.log('objArr', objArr);
console.log('strArr', strArr);