We have an array of objects
var items = [
{ id: 1, order_assigned: 2},
{ id: 2, order_assigned: 4},
{ id: 3, order_assigned: 1},
{ id: 4, order_assigned: 5},
{ id: 5, order_assigned: 3}
];
Each have id and some order number.
For example, user changes order number at id 2 to 0. Array now will look like this:
var items = [
{ id: 1, order_assigned: 2},
{ id: 2, order_assigned: 0},
{ id: 3, order_assigned: 1},
{ id: 4, order_assigned: 5},
{ id: 5, order_assigned: 3}
];
Now we need to reindex order_assigned in order to fill gaps in order_assigned order.
i.e. array should look like this
var items = [
{ id: 1, order_assigned: 2},
{ id: 2, order_assigned: 0},
{ id: 3, order_assigned: 1},
{ id: 4, order_assigned: 4},
{ id: 5, order_assigned: 3}
];
Item with id 4 changes order assigned number from 5 to 4, cos there is no item with 4 order assigned number.
Numbering in order_assigned should go in order from 1 to the last established rank. 1, 2, 3, 4. If someone enters 1,2,5,7 to order_assigned it must be converted to 1,2,3,4.
In other words, if there is a gap in order number, all digits after it must be recalculated. No resorting of items order itself needed.
Totally stucked how to do this right way. Please, help!
I think you're asking us to order this based on order_assigned, then close the gaps between the order_assigned.
I'm first sorting the array, then looping through it. I'm then replacing the order_assigned value with the current index.
var items = [
{ id: 1, order_assigned: 2},
{ id: 2, order_assigned: 0},
{ id: 3, order_assigned: 1},
{ id: 4, order_assigned: 5},
{ id: 5, order_assigned: 3}
];
items.sort(function(a, b) {
return a.order_assigned - b.order_assigned;
});
var counter = 0;
for (var index in items) {
if (items[index].order_assigned === 0) {
continue;
} // leave orders that are 0 the same
items[index].order_assigned = ++counter;
}
items.sort(function(a, b) {
return a.id - b.id;
}); // sort again on the ID field
console.log(items);
function sortCloseGap(array) {
return array.slice() // copy
.sort(function(a, b) { return a.order_assigned - b.order_assigned }) // sort
.map(function(item, index) { // assign new order
item.order_assigned = index + 1;
return item;
});
}
I hope you don't mind the mutability.
Related
This question builds on many similar ones like Construct hierarchy tree from flat list with parent field?
However the twist is that there is no parent id.
e.g.
[
{id: 1, depth: 1, ...},
{id: 2, depth: 2, ...},
{id: 3, depth: 3, ...},
{id: 4, depth: 2, ...},
{id: 5, depth: 1, ...},
{id: 6, depth: 2, ...},
{id: 7, depth: 2, ...},
{id: 8, depth: 1, ...},
{id: 9, depth: 2, ...},
{id: 10, depth: 3, ...},
{id: 11, depth: 3, ...},
]
What is a performant way to construct the following tree?
Note that the children always come after the parent i.e. one can see the tree from the depth value. For example, id 2 is a child of id 1 since its depth is 2 and id 1 has a depth of 1. id 3 is a child of id 2 since id 3 has a depth of 3. id 4 is a child of id 1 not id 3 because id 4 has a depth of 2 (a step up) from id 3's depth of 3
\\tree digram
1
2
3
4
5
6
7
8
9
10
11
Should have values like
[
{id:1, depth:1, children: [
{id: 2, depth: 2, children: [...]},
...
]},
{id:5, depth:1, children: [...]},
{id:6, depth:1, children: [...]},
]
You can use an array for this that has an index for each depth. At every moment, it will represent a path from the (virtual) root to the current node. When dealing with a node, its parent will sit at index depth-1, where it can be inserted in that parent's children property, and the node itself will be placed at index depth:
function createForest(flatdata) {
const path = [{ children: [] }];
for (const obj of flatdata) {
path[obj.depth - 1].children.push(path[obj.depth] = { ...obj, children: [] });
}
return path[0].children;
}
// demo
const flatdata = [{id: 1, depth: 1},{id: 2, depth: 2},{id: 3, depth: 3},{id: 4, depth: 2},{id: 5, depth: 1},{id: 6, depth: 2},{id: 7, depth: 2},{id: 8, depth: 1},{id: 9, depth: 2},{id: 10, depth: 3},{id: 11, depth: 3}];
const roots = createForest(flatdata);
console.log(roots);
Irregular depths
If the depth values do not correspond to the actual depth of the nodes, but leave gaps, then use a "dictionary" (a plain object) to record the mapping of the depth property values with which real depth they correspond with:
function createForest(flatdata) {
const path = [{ children: [] }];
const depthMap = { 0: 0 };
for (const obj of flatdata) {
path[(depthMap[obj.depth] ??= path.length) - 1].children.push(
path[depthMap[obj.depth]] = { ...obj, children: []}
);
}
return path[0].children;
}
// demo
const flatdata = [{id: 1, depth: 10},{id: 2, depth: 20},{id: 3, depth: 30},{id: 4, depth: 20},{id: 5, depth: 10},{id: 6, depth: 20},{id: 7, depth: 20},{id: 8, depth: 10},{id: 9, depth: 20},{id: 10, depth: 30},{id: 11, depth: 30}];
const roots = createForest(flatdata);
console.log(roots);
If however, the only irregularity is that the depth does not always start at 1, but sometimes at 2, it will be more efficient to prefix the input data with a dummy depth-one node, use the first function, and then remove the dummy "root" (with depth 1) from the result.
Go through the array and add each item to the tree as well as to a trail of breadcrumbs. Each next item either goes as a child to the last one or you backtrack through the breadcrumb trail to the correct depth where it needs to be inserted:
const peek = arr =>
arr[arr.length-1];
function toTree(arr) {
const tree = [];
const trail = [];
for (const item of arr) {
while ((peek(trail)?.depth ?? 0) >= item.depth) {
trail.pop();
}
const current = peek(trail)?.children ?? tree;
const treeNode = {...item, children: []};
current.push(treeNode);
trail.push(treeNode);
}
return tree;
}
const array = [
{id: 1, depth: 1, },
{id: 2, depth: 2, },
{id: 3, depth: 3, },
{id: 4, depth: 2, },
{id: 5, depth: 1, },
{id: 6, depth: 2, },
{id: 7, depth: 2, },
{id: 8, depth: 1, },
{id: 9, depth: 2, },
{id: 10, depth: 3 },
{id: 11, depth: 3 },
]
console.log(toTree(array));
This solution clones each item, in order to add the .children property. If no cloning is necessary, item can be directly mutated.
You could take an array of the last inserted objects.
const
data = [{ id: 1, depth: 1 }, { id: 2, depth: 2 }, { id: 3, depth: 3 }, { id: 4, depth: 2 }, { id: 5, depth: 1 }, { id: 6, depth: 2 }, { id: 7, depth: 2 }, { id: 8, depth: 1 }, { id: 9, depth: 2 }, { id: 10, depth: 3 }, { id: 11, depth: 3 }],
result = data.reduce((r, { depth, ...o }) => {
r[depth - 1].push({ ...o, children: r[depth] = [] });
return r;
}, [[]])[0];
console.log(result);
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The data structure that I am trying to achieve would look as so :
I would like the list_id to become a key in a object, and hold all the id's of the items that have the matching list id.
var lists = { (list_id)1 : [1, 2, 3]
(list_id)2 : [4, 5, 6]
(list_id)3 : [7, 8, 9]
(list_id)4 : [10, 11, 12] };
this object is created from a json data structure that looks like this:
let json = [{ id: 1, list_id: 1 }, { id: 2, list_id: 1 },
{id: 3, list_id: 1 }, {id: 4, list_id: 2 },
{id: 5, list_id: 2 }, {id: 6, list_id: 2 },
{id: 7, list_id: 3 }, {id: 8, list_id: 3 },
{id: 9, list_id: 3 }, {id: 10, list_id: 4 },
{id: 11, list_id: 4 }, {id: 12, list_id: 4 }]
I can make an object that holds all the list_id's as keys but am getting stumped on pushing the actions_id into the value pair array with the matching list id.
let listAll = {};
json.forEach(function(lista, index, listb) {
listAll[lista.list_id] = [];
if ( listAll[lista.list_id] === lista.list_id){
listAll[lista.list_id].push(lista.id)
} else {
listAll[lista.list_id] = [lista.id];
}
});
My goal is to have and object that contains a key for every list_id currently avaliable from the actions.
Then add every action that contains the matching list_id into a value pair array.
the current output of this code is
{ '1': [ 3 ], '2': [ 6 ], '3': [ 9 ], '4': [ 12 ] }
which does not contain all numbers, each array should contain 3 numbers.
An alternative is using the function reduce to group the objects by a specific key = ['list_id', list_id].join('').
let json = [{ id: 1, list_id: 1 }, { id: 2, list_id: 1 }, {id: 3, list_id: 1 }, {id: 4, list_id: 2 }, {id: 5, list_id: 2 }, {id: 6, list_id: 2 }, {id: 7, list_id: 3 }, {id: 8, list_id: 3 }, {id: 9, list_id: 3 }, {id: 10, list_id: 4 }, {id: 11, list_id: 4 }, {id: 12, list_id: 4 }],
result = json.reduce((a, {id, list_id}) => {
let key = ['list_id', list_id].join(''); // For example: this is creating ['list_id', 1] to list_id1
(a[key] || (a[key] = [])).push(id);
return a;
}, Object.create(null)/*This is only to create an object without prototype -> {}*/);
console.log(result);
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Why don't you try hasOwnProperty instead?
var listAll = {};
json.forEach(function(list, index) {
if (listAll.hasOwnProperty(list.list_id)) {
listAll[list.list_id].push(list.id);
}else {
listAll[list.list_id] = [list.id];
}
});
console.log(listAll);
I'm trying to iterate over an existing array with of objects with a 'quantity' property and rebuild it by a control value.
let cart = [{id: 1, name: 'Pizza', quantity: 5, specialId: 0},
{id: 2, name: 'Burger', quantity: 2, specialId: 0}];
I have a control of 3 items i.e. for every 3 items you get a discount so I'd like to reconstitute the cart array as follows:
cart = [{id: 1, name: 'Pizza', quantity: 3, specialId: 1},
{id: 2, name: 'Pizza', quantity: 2, specialId: 2},
{id: 3, name: 'Burger', quantity: 1, specialId: 2},
{id: 4, name: 'Burger', qty: 1, specialId: 0}]
I've looked at several ways of doing this mostly around creating a new array of single quantity items and then creating another final array but surely that isn't very efficient?
I'd appreciate any pointers. I have a horrible feeling I'm missing something simple and have stared at this too long.
If I understand correctly the amount of three is ignorant of the type of product, so the second batch of three (in your example) consists of 2 pizzas and 1 burger.
The specialId seems to be unique and non-zero for every complete set of three (where every item in that set shares that specialId value), and zero for any remaining item(s).
Finally, it seems that the id in the result is unrelated to the input, but just an incremental number.
Here is how you could do that:
function splitBy(cart, size) {
const result = [];
let quantity = 0;
let grab = size;
let specialId = 1;
let id = 1;
for (let item of cart) {
for (quantity = item.quantity; quantity >= grab; quantity -= grab, grab = size, specialId++) {
if (result.length && !result[result.length-1].specialId) result[result.length-1].specialId = specialId;
result.push(Object.assign({}, item, {quantity: grab, specialId, id: id++}));
}
if (quantity) result.push(Object.assign({}, item, {quantity, specialId: 0, id: id++}));
grab = size - quantity;
}
return result;
}
const cart = [{id: 1, name: 'Pizza', quantity: 5, specialId: 0},
{id: 2, name: 'Burger', quantity: 2, specialId: 0}];
const result = splitBy(cart, 3)
console.log(result);
Basically you have two options.
loop over the current cart, and if the quantity is over 3, split it to two, and push them both.
split the array, and then merge it together.
My guess is to go with the first option, doing something like this:
var cart = [{id: 1, name: 'Pizza', quantity: 5, specialId: 0},
{id: 2, name: 'Burger', quantity: 2, specialId: 0}];
var a = [];
cart.forEach(x => {
if (x.quantity > 3) {
let temp = {...x};
temp.quantity = 3;
a.push(temp);
x.quantity -= 3;
}
a.push(x)
});
I am trying to remove duplicate objects from an array, and keep only the objects which have the highest nb value.
Example:
From this array:
let arr = [
{id: 1, nb: 1},
{id: 1, nb: 4},
{id: 2, nb: 1},
{id: 3, nb: 1},
{id: 1, nb: 2},
{id: 1, nb: 3},
{id: 2, nb: 7},
{id: 2, nb: 8},
];
I am supposed to get this:
arr2 = [
{ id: 1, nb: 4 },
{ id: 2, nb: 8 },
{ id: 3, nb: 1 }
]
The algorithm below is very correct in theory, however I see the original array is modified by the end (see the last console.log(arr) below):
Code:
let arr = [
{id: 1, nb: 1},
{id: 1, nb: 4},
{id: 2, nb: 1},
{id: 3, nb: 1},
{id: 1, nb: 2},
{id: 1, nb: 3},
{id: 2, nb: 7},
{id: 2, nb: 8},
];
// Original array
console.log(arr);
let tmp = {};
for(let i=0; i<arr.length; i++) {
if( !tmp[arr[i].id] ) {
tmp[arr[i].id] = arr[i];
} else {
if (tmp[arr[i].id].nb < arr[i].nb ) {
tmp[arr[i].id].nb = arr[i].nb;
}
}
}
var result = Object.values(tmp);
// This output the desired result
console.log(result);
// Why the original array changed ?
console.log(arr);
This will output:
> Array [Object { id: 1, nb: 1 }, Object { id: 1, nb: 4 }, Object { id: 2, nb: 1 }, Object { id: 3, nb: 1 }, Object { id: 1, nb: 2 }, Object { id: 1, nb: 3 }, Object { id: 2, nb: 7 }, Object { id: 2, nb: 8 }]
> Array [Object { id: 1, nb: 4 }, Object { id: 2, nb: 8 }, Object { id: 3, nb: 1 }]
> Array [Object { id: 1, nb: 4 }, Object { id: 1, nb: 4 }, Object { id: 2, nb: 8 }, Object { id: 3, nb: 1 }, Object { id: 1, nb: 2 }, Object { id: 1, nb: 3 }, Object { id: 2, nb: 7 }, Object { id: 2, nb: 8 }]
Why did the original array changed when there is no processing on it apart from looping?
The original array is updated at last as the objects in your tmp map and arr share the same object reference. So changes made in tmp will be reflected in arr. You can use Object.assign() to make them point to separate reference. Try the following:
let arr = [ {id: 1, nb: 1}, {id: 1, nb: 4}, {id: 2, nb: 1}, {id: 3, nb: 1}, {id: 1, nb: 2}, {id: 1, nb: 3}, {id: 2, nb: 7}, {id: 2, nb: 8}, ];
let tmp = {};
for(let i=0; i<arr.length; i++) {
if( !tmp[arr[i].id] ) {
tmp[arr[i].id] = Object.assign({},arr[i]);
} else {
if (tmp[arr[i].id].nb < arr[i].nb ) {
tmp[arr[i].id].nb = arr[i].nb;
}
}
}
var result = Object.values(tmp);
console.log(result)
Because objects in both the arrays are sharing the same reference.
You will need to update from
tmp[arr[i].id] = arr[i];
to
tmp[arr[i].id] = JSON.parse(JSON.stringify(arr[i]));
let arr = [
{id: 1, nb: 1},
{id: 1, nb: 4},
{id: 2, nb: 1},
{id: 3, nb: 1},
{id: 1, nb: 2},
{id: 1, nb: 3},
{id: 2, nb: 7},
{id: 2, nb: 8},
];
let tmp = {};
for(let i=0; i<arr.length; i++) {
if( !tmp[arr[i].id] ) {
tmp[arr[i].id] = JSON.parse(JSON.stringify(arr[i]));
} else {
if (tmp[arr[i].id].nb < arr[i].nb ) {
tmp[arr[i].id].nb = arr[i].nb;
}
}
}
var result = Object.values(tmp);
console.log(arr); // original array unchanged
Is there a way to compare differences between arrays based on changes on their elements positions?
I have an original array of objects which undergoes a change on one of it's element's values, this change is mapped into a new array:
origElements = [{id: 1, value: 50},
{id: 2, value: 60},
{id: 3, value: 70}]
changedElements = [{id: 1, value: 50},
{id: 3, value: 60},
{id: 2, value: 120}]
var diff = _.difference(_.pluck(origElements, "id"), _.pluck(changedElements, "id"));
var result = _.filter(origElements, function(obj) { return diff.indexOf(obj.id) >= 0; });
In this case it is clear why 'result' would return nothing. As there's no difference of values between: [1, 2, 3] and [1, 3, 2]. What I'm trying to achieve here is a 'strict difference' which would look at index as well, thus returning some reference to the new order of the objects.
How about doing it this way:
var origElements = [{
id: 1,
value: 50
}, {
id: 2,
value: 60
}, {
id: 3,
value: 70
}];
var changedElements = [{
id: 1,
value: 50
}, {
id: 3,
value: 60
}, {
id: 2,
value: 120
}];
var origElementsIds = _.pluck(origElements, "id");
var changedElementsIds = _.pluck(changedElements, "id");
console.log("Are array element positions same ?",
origElementsIds.join() === changedElementsIds.join());