Replace FOR to add all values in an array [duplicate]

Replace FOR to add all values in an array [duplicate] - javascript

This question already has answers here:
Better way to sum a property value in an array
(20 answers)
Sum up array with objects
(4 answers)
Closed 3 years ago.
I'm using Javascript, and I have an array like this:
counters: [
{ id: 1, value: 0 },
{ id: 2, value: 10 },
{ id: 3, value: 5 },
{ id: 4, value: 3 }
]
I want to get a variable total, with the sum of every value field in the counters array. Right now I'm doing:
Total() {
let total = 0;
for (let i = 0; i < counters.length; i++) {
total += counters[i].value;
}
return total;
}
Even if that works, I know that there's a better way. I tried reduce method, but I couldn't get what I need. How can I do it?

You could add the destructured value with Array#reduce.
var object = { counters: [{ id: 1, value: 0 }, { id: 2, value: 10 }, { id: 3, value: 5 }, { id: 4, value: 3 }] },
sum = object.counters.reduce((s, { value }) => s + value, 0);
console.log(sum);

const counters = [
{ id: 1, value: 0 },
{ id: 2, value: 10 },
{ id: 3, value: 5 },
{ id: 4, value: 3 }
]
const total = counters.map(x => x.value).reduce((a,c) => a +c)
console.log(total)
map your array to represent only the value property and use reduce
const total = counters.map(x => x.value).reduce((a,c) => a + c)

You can do it with reduce, simply pass in a default value of 0:
counters = [
{ id: 1, value: 0 },
{ id: 2, value: 10 },
{ id: 3, value: 5 },
{ id: 4, value: 3 }
]
total = counters.reduce((accumulator, counter) => accumulator + counter.value, 0);
console.log(total);

the simplest way is to use reduce method
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce
;)
const total = counters.reduce((acc, curr) => acc + curr.value, 0);

Related

Find objects with same prop and return the update value with its associated prop [duplicate]

I have javascript array object as below. My need is to sum value base on seach id in the array object.
var array = [
{ id: 1, val: 10 },
{ id: 2, val: 25 },
{ id: 3, val: 20 },
{ id: 1, val: 30 },
{ id: 1, val: 25 },
{ id: 2, val: 10 },
{ id: 1, val: 20 }
],
For example sum of value for id 1 is 10 + 30 + 25 + 20 = 85 , It may be something link linq but I'm not sure in javascript. Thanks for all answers.

You can use a combination of filter and reduce to get the result you want:
sumOfId = (id) => array.filter(i => i.id === id).reduce((a, b) => a + b.val, 0);
Usage:
const sumOf1 = sumOfId(1); //85
Reading material:
Array.prototype.filter
Array.prototype.reduce

A way to do it with a traditional for loop
var array = [
{ id: 1, val: 10 },
{ id: 2, val: 25 },
{ id: 3, val: 20 },
{ id: 1, val: 30 },
{ id: 1, val: 25 },
{ id: 2, val: 10 },
{ id: 1, val: 20 }
];
var sums = {};
for (var i = 0; i < array.length; i++) {
var obj = array[i];
sums[obj.id] = sums[obj.id] === undefined ? 0 : sums[obj.id];
sums[obj.id] += parseInt(obj.val);
}
console.log(sums);
running example

You can use reduce() and findIndex()
var array = [
{ id: 1, val: 10 },
{ id: 2, val: 25 },
{ id: 3, val: 20 },
{ id: 1, val: 30 },
{ id: 1, val: 25 },
{ id: 2, val: 10 },
{ id: 1, val: 20 }
];
let res = array.reduce((ac,a) => {
let ind = ac.findIndex(x => x.id === a.id);
ind === -1 ? ac.push(a) : ac[ind].val += a.val;
return ac;
},[])
console.log(res);

JS noob here ... I guess something like this should be here too :-)
let newArray = {}
array.forEach((e) => {
!newArray[e.id] && (newArray[e.id] = 0);
newArray[e.id] += e.val;
});

You can loop on the array and check the ids.
var array = [
{ id: 1, val: 10 },
{ id: 2, val: 25 },
{ id: 3, val: 20 },
{ id: 1, val: 30 },
{ id: 1, val: 25 },
{ id: 2, val: 10 },
{ id: 1, val: 20 }
];
var sum = 0;
var id = 1;
$.each(array, function(index, object){
if (object.id == id) {
sum += object.val;
}
});
console.log(sum);
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

Using Array#reduce and Map you can get the sum for each id like so. This also uses destructuring to have quicker access to properties.
const data=[{id:1,val:10},{id:2,val:25},{id:3,val:20},{id:1,val:30},{id:1,val:25},{id:2,val:10},{id:1,val:20}];
const res = data.reduce((a,{id,val})=>{
return a.set(id, (a.get(id)||0) + val);
}, new Map())
console.log(res.get(1));
console.log(res.get(2));
If you wanted to output all the sums, then you need to use Array#from
const data=[{id:1,val:10},{id:2,val:25},{id:3,val:20},{id:1,val:30},{id:1,val:25},{id:2,val:10},{id:1,val:20}];
const res = Array.from(
data.reduce((a,{id,val})=>{
return a.set(id, (a.get(id)||0) + val);
}, new Map())
);
console.log(res);
If the format should be similar as to your original structure, you need to add a Array#map afterwards to transform it.
const data=[{id:1,val:10},{id:2,val:25},{id:3,val:20},{id:1,val:30},{id:1,val:25},{id:2,val:10},{id:1,val:20}];
const res = Array.from(
data.reduce((a,{id,val})=>{
return a.set(id, (a.get(id)||0) + val);
}, new Map())
).map(([id,sum])=>({id,sum}));
console.log(res);

You could take GroupBy from linq.js with a summing function.
var array = [{ id: 1, val: 10 }, { id: 2, val: 25 }, { id: 3, val: 20 }, { id: 1, val: 30 }, { id: 1, val: 25 }, { id: 2, val: 10 }, { id: 1, val: 20 }],
result = Enumerable
.From(array)
.GroupBy(null, null, "{ id: $.id, sum: $$.Sum('$.val') }", "$.id")
.ToArray();
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/linq.js/2.2.0.2/linq.js"></script>

Here is another option, introducing an Array.prototype.sum helper:
Array.prototype.sum = function (init = 0, fn = obj => obj) {
if (typeof init === 'function') {
fn = init;
init = 0;
}
return this.reduce(
(acc, ...fnArgs) => acc + fn(...fnArgs),
init
);
};
// .sum usage examples
console.log(
// sum simple values
[1, 2, 3].sum(),
// sum simple values with initial value
[1, 2, 3].sum(10),
// sum objects
[{ a: 1 }, { a: 2 }, { a: 3 }].sum(obj => obj.a),
// sum objects with initial value
[{ a: 1 }, { a: 2 }, { a: 3 }].sum(10, obj => obj.a),
// sum custom combinations
[{ amount: 1, price: 2 }, { amount: 3, price: 4 }]
.sum(product => product.amount * product.price)
);
var array = [{ id: 1, val: 10 }, { id: 2, val: 25 }, { id: 3, val: 20 }, { id: 1, val: 30 }, { id: 1, val: 25 }, { id: 2, val: 10 }, { id: 1, val: 20 }];
// solutions
console.log(
array.filter(obj => obj.id === 1).sum(obj => obj.val),
array.filter(({id}) => id === 1).sum(({val}) => val),
array.sum(({id, val}) => id === 1 ? val : 0)
);
references:
Array.prototype.reduce
Array.prototype.filter
Arrow functions used in sum(obj => obj.val)
Object destructing assignment used in ({id}) => id === 1
Rest parameters used in (acc, ...fnArgs) => acc + fn(...fnArgs)
Conditional (ternary) operator used in id === 1 ? val : 0

Comparing array elements against the rest of the array

The question might be a bit vague, but I'll explain the result I'm expecting to get with an example.
Say I have the following array made out of objects with the following shape:
[
{
id: 1,
value: 10
},
{
id: 2,
value: 100
},
{
id: 3,
value: 10
},
{
id: 4,
value: 10
},
{
id: 5,
value: 1000
},
]
This array might contain hundrends, maybe thousands of entries, but for simplicity, I'll keep it small.
What I'm trying to achieve is compare the value property of every object with the other value properties and assign a new property duplicate with a boolean value to that specific object.
Given the example above, I would expect to receive an array with the following members:
[
{
id: 1,
value: 10,
duplicate: true
},
{
id: 2,
value: 100
},
{
id: 3,
value: 10,
duplicate: true
},
{
id: 4,
value: 10,
duplicate: true
},
{
id: 5,
value: 1000
},
]
Whats the most optimal way I could implement this behavior ?
Thank you.

I'd do a single pass through the array remembering the first seen entry with a given value in a Map, marking that first entry (and any others) as duplicates if it's present, like this:
const map = new Map();
for (const entry of array) {
const previous = map.get(entry.value);
if (previous) {
previous.duplicate = entry.duplicate = true;
} else {
map.set(entry.value, entry);
}
}
Live Example:
const array = [
{
id: 1,
value: 10
},
{
id: 2,
value: 100
},
{
id: 3,
value: 10
},
{
id: 4,
value: 10
},
{
id: 5,
value: 1000
},
];
const map = new Map();
for (const entry of array) {
const previous = map.get(entry.value);
if (previous) {
previous.duplicate = entry.duplicate = true;
} else {
map.set(entry.value, entry);
}
}
console.log(array);

You can do this by first determining which are the duplicates, and then setting the 'duplicate' attribute.
counts = items.reduce((counter, item) => {
if (counter[item.value] != null) {
counter[item.value] += 1;
} else {
counter[item.value] = 1;
}
return counter;
}, {});
After this, you can go over your items, and if the count is >=2, set the 'duplicate' attribute.
items.forEach((item) => {
if (counter[item.value] > 1) {
item['duplicate'] = true;
}
});

You can use Array.map and Array.filter for that.
const input = [
{ id: 1, value: 10 },
{ id: 2, value: 100 },
{ id: 3, value: 10 },
{ id: 4, value: 10 },
{ id: 5, value: 1000 }
]
const output = input.map(entry => {
if (input.filter(x => x.value === entry.value).length > 1) {
return {
duplicate: true,
...entry
}
}
return entry
})
console.log(output)

I would create a map with value as the key, and a list of ids as the values, than after iterating over the whole map and creating the new mapping, unpack it back tothe desired form, and add duplicated for keys with more than one value.

I think this will help you. arr is your array.
arr.forEach(e=> {
const dublicatedDataLenth = arr.filter(a => a.value == e.value).length;
if(dublicatedDataLenth > 1){
e.dublicate = true;
}
})
It should be what you are looking for.

A copy from myself with a single loop and an object for storing seen values.
This approach returns a new array and does not mutate the given data.
var data = [{ id: 1, value: 10 }, { id: 2, value: 100 }, { id: 3, value: 10 }, { id: 4, value: 10 }, { id: 5, value: 1000 }],
result = data.map((seen => ({ ...o }) => {
if (o.value in seen) {
o.duplicate = true;
if (seen[o.value]) {
seen[o.value].duplicate = true;
seen[o.value] = false;
}
} else seen[o.value] = o;
return o;
})({}));
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

How to check whether two Objects has few of the matching data in JavaScript

I have data like this:
Array = [
{ 0: { Id: 18, Time: 3 } },
{ 1: { Id: 5, Time: 7 } },
{ 2: { Id: 18, Time: 10 } },
{ 3: { Id: 2, Time: 9 } },
];
As you can see Object 0 & Object 2 has same Id.
I want to perform an operation which will check whether any of the Objects has same Id in it and return true or false.

The below code might help.
function getMatch(array) {
var idArray = array.map(a => a.Id);
return idArray.some((a, index) => idArray.indexOf(a) !== index);
}
var arr = [
{ Id: 18, Time: 3 },
{ Id: 5, Time: 7 },
{ Id: 18, Time: 10 },
{ Id: 2, Time: 9 }
];
console.log(getMatch(arr));

You can map your array of objects its entries, and then map the entires to its Id to get an array of Ids. You can put this array of ids into a set to remove duplicates and compare it with the length of the array to check if an Id was removed when creating the set.
const arr = [{ 0: { Id: 18, Time: 3 } }, { 1: { Id: 5, Time: 7 } }, { 2: { Id: 18, Time: 10 } }, { 3: { Id: 2, Time: 9 } }];
const ids = arr.map(Object.values).map(([{Id}]) => Id);
const hasSameId = ids.length !== new Set(ids).size;
console.log(hasSameId);

Use this function which will tell same id exist in your array.
SameIdMatch() {
let idList = [];
for (let i = 0; i < Array.length; i++) {
if(idList.indexOf(Array[i].Id) === -1) {
idList.push(Array[i].Id);
return true;
} else {
return false;
}
}
}

Try this one liner.
const input = [
{ 0: { Id: 18, Time: 3 } },
{ 1: { Id: 5, Time: 7 } },
{ 2: { Id: 18, Time: 10 } },
{ 3: { Id: 2, Time: 9 } }
];
const hasDuplicate = input.length !== [...new Set(input.map((item, index) => item[index].Id))].length;
console.log(hasDuplicate);

Lodash. How to get aggregate array from array objects

For example, I have an array:
const reference = [{id: 1, value: 10}, {id: 2, value: 10}, {id: 3, value: 10}, {id: 4, value: 5}];
How to get an array values from reference like
const result = [0, 10, 20, 25];
First step always = 0
Second step 0 + 10 = 10
Third step 0 + 10 + 10 = 20
Forth step 0 + 10 + 10 + 5 = 25

You can reduce the array, and add the current value to the last sum:
const reference = [{id: 1, value: 10}, {id: 2, value: 10}, {id: 3, value: 10}, {id: 4, value: 5}];
const result = reference
.reduce((r, o, i) => {
r.push(i === 0 ? 0 : r[r.length - 1] + o.value);
return r;
}, [])
console.log(result);

You could map the values by taking a closure over the sum and take zero for the first element.
const
reference = [{ id: 1, value: 10 }, { id: 2, value: 10 }, { id: 3, value: 10 }, { id: 4, value: 5 }],
result = reference.map((sum => ({ value }, i) => sum += i && value)(0));
console.log(result);

The way I would do this would be by using the Array.reduce method as follows :
let result = [0]
reference.reduce((acc, cur) => {
result.push(Object.values(cur)[1]+result[result.length-1])
})
Hope it helps

How to sum value in javascript array object form specific search id?

I have javascript array object as below. My need is to sum value base on seach id in the array object.
var array = [
{ id: 1, val: 10 },
{ id: 2, val: 25 },
{ id: 3, val: 20 },
{ id: 1, val: 30 },
{ id: 1, val: 25 },
{ id: 2, val: 10 },
{ id: 1, val: 20 }
],
For example sum of value for id 1 is 10 + 30 + 25 + 20 = 85 , It may be something link linq but I'm not sure in javascript. Thanks for all answers.

You can use a combination of filter and reduce to get the result you want:
sumOfId = (id) => array.filter(i => i.id === id).reduce((a, b) => a + b.val, 0);
Usage:
const sumOf1 = sumOfId(1); //85
Reading material:
Array.prototype.filter
Array.prototype.reduce

A way to do it with a traditional for loop
var array = [
{ id: 1, val: 10 },
{ id: 2, val: 25 },
{ id: 3, val: 20 },
{ id: 1, val: 30 },
{ id: 1, val: 25 },
{ id: 2, val: 10 },
{ id: 1, val: 20 }
];
var sums = {};
for (var i = 0; i < array.length; i++) {
var obj = array[i];
sums[obj.id] = sums[obj.id] === undefined ? 0 : sums[obj.id];
sums[obj.id] += parseInt(obj.val);
}
console.log(sums);
running example

You can use reduce() and findIndex()
var array = [
{ id: 1, val: 10 },
{ id: 2, val: 25 },
{ id: 3, val: 20 },
{ id: 1, val: 30 },
{ id: 1, val: 25 },
{ id: 2, val: 10 },
{ id: 1, val: 20 }
];
let res = array.reduce((ac,a) => {
let ind = ac.findIndex(x => x.id === a.id);
ind === -1 ? ac.push(a) : ac[ind].val += a.val;
return ac;
},[])
console.log(res);

JS noob here ... I guess something like this should be here too :-)
let newArray = {}
array.forEach((e) => {
!newArray[e.id] && (newArray[e.id] = 0);
newArray[e.id] += e.val;
});

You can loop on the array and check the ids.
var array = [
{ id: 1, val: 10 },
{ id: 2, val: 25 },
{ id: 3, val: 20 },
{ id: 1, val: 30 },
{ id: 1, val: 25 },
{ id: 2, val: 10 },
{ id: 1, val: 20 }
];
var sum = 0;
var id = 1;
$.each(array, function(index, object){
if (object.id == id) {
sum += object.val;
}
});
console.log(sum);
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

Using Array#reduce and Map you can get the sum for each id like so. This also uses destructuring to have quicker access to properties.
const data=[{id:1,val:10},{id:2,val:25},{id:3,val:20},{id:1,val:30},{id:1,val:25},{id:2,val:10},{id:1,val:20}];
const res = data.reduce((a,{id,val})=>{
return a.set(id, (a.get(id)||0) + val);
}, new Map())
console.log(res.get(1));
console.log(res.get(2));
If you wanted to output all the sums, then you need to use Array#from
const data=[{id:1,val:10},{id:2,val:25},{id:3,val:20},{id:1,val:30},{id:1,val:25},{id:2,val:10},{id:1,val:20}];
const res = Array.from(
data.reduce((a,{id,val})=>{
return a.set(id, (a.get(id)||0) + val);
}, new Map())
);
console.log(res);
If the format should be similar as to your original structure, you need to add a Array#map afterwards to transform it.
const data=[{id:1,val:10},{id:2,val:25},{id:3,val:20},{id:1,val:30},{id:1,val:25},{id:2,val:10},{id:1,val:20}];
const res = Array.from(
data.reduce((a,{id,val})=>{
return a.set(id, (a.get(id)||0) + val);
}, new Map())
).map(([id,sum])=>({id,sum}));
console.log(res);

You could take GroupBy from linq.js with a summing function.
var array = [{ id: 1, val: 10 }, { id: 2, val: 25 }, { id: 3, val: 20 }, { id: 1, val: 30 }, { id: 1, val: 25 }, { id: 2, val: 10 }, { id: 1, val: 20 }],
result = Enumerable
.From(array)
.GroupBy(null, null, "{ id: $.id, sum: $$.Sum('$.val') }", "$.id")
.ToArray();
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/linq.js/2.2.0.2/linq.js"></script>

Here is another option, introducing an Array.prototype.sum helper:
Array.prototype.sum = function (init = 0, fn = obj => obj) {
if (typeof init === 'function') {
fn = init;
init = 0;
}
return this.reduce(
(acc, ...fnArgs) => acc + fn(...fnArgs),
init
);
};
// .sum usage examples
console.log(
// sum simple values
[1, 2, 3].sum(),
// sum simple values with initial value
[1, 2, 3].sum(10),
// sum objects
[{ a: 1 }, { a: 2 }, { a: 3 }].sum(obj => obj.a),
// sum objects with initial value
[{ a: 1 }, { a: 2 }, { a: 3 }].sum(10, obj => obj.a),
// sum custom combinations
[{ amount: 1, price: 2 }, { amount: 3, price: 4 }]
.sum(product => product.amount * product.price)
);
var array = [{ id: 1, val: 10 }, { id: 2, val: 25 }, { id: 3, val: 20 }, { id: 1, val: 30 }, { id: 1, val: 25 }, { id: 2, val: 10 }, { id: 1, val: 20 }];
// solutions
console.log(
array.filter(obj => obj.id === 1).sum(obj => obj.val),
array.filter(({id}) => id === 1).sum(({val}) => val),
array.sum(({id, val}) => id === 1 ? val : 0)
);
references:
Array.prototype.reduce
Array.prototype.filter
Arrow functions used in sum(obj => obj.val)
Object destructing assignment used in ({id}) => id === 1
Rest parameters used in (acc, ...fnArgs) => acc + fn(...fnArgs)
Conditional (ternary) operator used in id === 1 ? val : 0

We Keep Coding

JavaScript is the programming language of the Web.

Replace FOR to add all values in an array [duplicate] - javascript

You could add the destructured value with Array#reduce. var object = { counters: [{ id: 1, value: 0 }, { id: 2, value: 10 }, { id: 3, value: 5 }, { id: 4, value: 3 }] }, sum = object.counters.reduce((s, { value }) => s + value, 0); console.log(sum);

You can do it with reduce, simply pass in a default value of 0: counters = [ { id: 1, value: 0 }, { id: 2, value: 10 }, { id: 3, value: 5 }, { id: 4, value: 3 } ] total = counters.reduce((accumulator, counter) => accumulator + counter.value, 0); console.log(total);

the simplest way is to use reduce method https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce ;) const total = counters.reduce((acc, curr) => acc + curr.value, 0);

Related

Find objects with same prop and return the update value with its associated prop [duplicate]

Comparing array elements against the rest of the array

How to check whether two Objects has few of the matching data in JavaScript

Lodash. How to get aggregate array from array objects

How to sum value in javascript array object form specific search id?

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