Remove Duplicates Form an Array

Remove duplicate values from JS array

Quick and dirty using jQuery:

var names = ["Mike","Matt","Nancy","Adam","Jenny","Nancy","Carl"];
var uniqueNames = [];
$.each(names, function(i, el){
    if($.inArray(el, uniqueNames) === -1) uniqueNames.push(el);
});

Removing duplicate elements from an array in Swift

You can roll your own, e.g. like this:

func unique<S : Sequence, T : Hashable>(source: S) -> [T] where S.Iterator.Element == T {
    var buffer = [T]()
    var added = Set<T>()
    for elem in source {
        if !added.contains(elem) {
            buffer.append(elem)
            added.insert(elem)
        }
    }
    return buffer
}

let vals = [1, 4, 2, 2, 6, 24, 15, 2, 60, 15, 6]
let uniqueVals = uniq(vals) // [1, 4, 2, 6, 24, 15, 60]

And as an extension for Array:

extension Array where Element: Hashable {
    func uniqued() -> Array {
        var buffer = Array()
        var added = Set<Element>()
        for elem in self {
            if !added.contains(elem) {
                buffer.append(elem)
                added.insert(elem)
            }
        }
        return buffer
    }
}

Or more elegantly (Swift 4/5):

extension Sequence where Element: Hashable {
    func uniqued() -> [Element] {
        var set = Set<Element>()
        return filter { set.insert($0).inserted }
    }
}

Which would be used:

[1,2,4,2,1].uniqued()  // => [1,2,4]

Remove duplicate from array of objects based on value of properties in JavaScript

You can use Map to club values by name and in case there are two values with same name just use the one without type = "new"

let someArray = [{id: 3, name:"apple", type: "new"}, {id: 1, name:"apple"}, {id: 2, name:"mango"}, {id: 4, name:"orange"}, {id: 5, name:"orange", type: "new"}, {id: 6, name: "pineapple", type: "new"}]

function getUnique(arr){
  let mapObj = new Map()
  
  arr.forEach(v => {
    let prevValue = mapObj.get(v.name)
    if(!prevValue || prevValue.type === "new"){
      mapObj.set(v.name, v)
    } 
  })
  return [...mapObj.values()]
}

console.log(getUnique(someArray))

Remove duplicates from an array in BigQuery

If you want to deduplicate an array in BigQuery, 1) you first have to flatten the array. 2) Subsequently, deduplication can be done as usual (e.g. using distinct or grouping etc.) 3) Finally, to return an array (as the original schema), we can group on the primary key and use ARRAY_AGG.

1) Flattening of the array is done using the UNNEST operator.

The UNNEST operator takes an ARRAY and returns a table, with one row for each element in the ARRAY.

In combination with a CROSS JOIN, we retrieve a row for each array record. (Note, the comma implies a CROSS JOIN, see docs)

SELECT 
  order_id,
  item.sku AS item_sku,
  item.price AS item_price
FROM data, UNNEST(items) AS item

2) Using DISTINCT we retrieve unique records.

SELECT DISTINCT
  order_id,
  item.sku AS item_sku,
  item.price AS item_price
FROM data, UNNEST(items) AS item

3) We can group on the primary key (order_id) and use ARRAY_AGG to return the results as array. I.e., returning the original schema.

SELECT 
  order_id,
  ARRAY_AGG(
    STRUCT(
      item_sku AS sku,
      item_price AS price
    ) 
  ) AS item
FROM flattened
GROUP BY order_id

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Full reproducible example

WITH data AS (
  SELECT 
    123 AS order_id,
    [
      STRUCT(
        'ABC' AS sku,
        5.99 AS price
      ),
      STRUCT(
        'ABC' AS sku,
        5.99 AS price
      ),
      STRUCT(
        'XYZ' AS sku,
        19.99 AS price
      )
    ] AS items,
  
  UNION ALL
  
  SELECT 
    456, 
    [
      STRUCT(
        'ABC' AS sku,
        5.99 AS price
      )
    ]
    
  UNION ALL
  
  SELECT 
    789, 
    [
      STRUCT(
        'XYZ' AS sku,
        19.99 AS price
      )
    ]
),

flattened AS (
  SELECT DISTINCT
    order_id,
    item.sku AS item_sku,
    item.price AS item_price
  FROM data, UNNEST(items) AS item
)

SELECT 
  order_id,
  ARRAY_AGG(
    STRUCT(
      item_sku AS sku,
      item_price AS price
    ) 
  ) AS item
FROM flattened
GROUP BY order_id

how to remove first element of duplicate in an array of objects

This will give you an array with the last value for duplicated elements, in preserved order. If you want exactly the 2nd one you need an extra flag

array=[{id:34,value:45}, {id:23,value:35}, {id:34,value:28}]

const obj = array.reduce ( (acc,cur,index) => {
  acc[cur.id] = {index:cur};
  return acc;
},{});

const output = Object.values(obj).sort( (a,b) => a.index - b.index).map( ({index:val}) => val )

console.log(output)

I need to remove duplicate products in an Array and sum their quantity in JavaScript

You can try the below approach to achieve this. Create an object (productsCheck in my case) and loop through the productsAll array. If the name already exists in the object then add the quantity, else simple add the product to your object ( i.e productsCheck)

Working code:

const productsAll = [{
    name: 'Product 1',
    ean: '1112223334445',
    sku: '4445',
    product_id: '70604566',
    quantity: 1,
  },
  {
    name: 'Product 1',
    ean: '1112223334445',
    sku: '4445',
    product_id: '70604566',
    quantity: 3,
  },
  {
    name: 'Product 2',
    ean: '1112223334446',
    sku: '4446',
    product_id: '60404533',
    quantity: 2,
  },
  {
    name: 'Product 3',
    ean: '1112223334447',
    sku: '4447',
    product_id: '30504512',
    quantity: 8,
  },
];

const productsCheck = {}

productsAll.forEach(product => {
  if (product.name in productsCheck) {
    productsCheck[product.name].quantity += product.quantity
  } else {
    productsCheck[product.name] = product
  }
})

console.log(productsCheck)

Remove duplicate objects from an Array

This one will assign this.subMenuItems an array containing only the first instance of each item because indexOf returns the first index where the object is found.

this.subMenuItems = this.items.filter((item, index, self) => self.indexOf(item) === index);

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