Removing all repetitions from an array in JavaScript

Question

Removing all repetitions from an array in JavaScript

My collection of objects includes the following inputs:

var jsonArray1 = [{id:'1',name:'John'},{id:'2',name:'Smith'},{id:'3',name:'Adam'},{id:'1',name:'John'}]

There is a duplicate id '1' that I would like to eliminate from my output. The desired result should be:

[{id:'2',name:'Smith'},{id:'3',name:'Adam'}]

I am seeking guidance on how to remove all duplicate records from the array. Can you provide me with direction on this?

javascript arrays json duplicates

Answer 1

Answer №1

To create a Map using an array, designate the key of the Map as your desired id. Duplicate entries will not be preserved (only the last occurrence will). Then, extract the values from the Map.

If you want to remove all instances of duplicates (as specified by the original poster):

const input = [{id:'1',name:'John'},
               {id:'2',name:'Smith'},
               {id:'3',name:'Adam'},
               {id:'1',name:'John'}]

const result = input.filter((x, i, arr) => 
                          arr.filter(e => e.id === x.id).length === 1)
console.log(result)

To retain one occurrence of duplicates:

const input = [{id:'1',name:'John'},
               {id:'2',name:'Smith'},
               {id:'3',name:'Adam'},
               {id:'1',name:'John'}]

const uniqueEntries = [...new Map(input.map(item => [item.id, item])).values()]
console.log(uniqueEntries)

Answer 2

To create a Map using an array, designate the key of the Map as your desired id. Duplicate entries will not be preserved (only the last occurrence will). Then, extract the values from the Map.

If you want to remove all instances of duplicates (as specified by the original poster):

const input = [{id:'1',name:'John'},
               {id:'2',name:'Smith'},
               {id:'3',name:'Adam'},
               {id:'1',name:'John'}]

const result = input.filter((x, i, arr) => 
                          arr.filter(e => e.id === x.id).length === 1)
console.log(result)

To retain one occurrence of duplicates:

const input = [{id:'1',name:'John'},
               {id:'2',name:'Smith'},
               {id:'3',name:'Adam'},
               {id:'1',name:'John'}]

const uniqueEntries = [...new Map(input.map(item => [item.id, item])).values()]
console.log(uniqueEntries)

Removing all repetitions from an array in JavaScript

Answer №1

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