How to compare each object in an array with each other. When found update the object with a new property

问题

For example consider the following array with objects.

var collection = [{name:'user1',phone:'203'},
                  {name:'user2',phone:'5050'},
                  {name:'user1',phone:'203'}]

Now I want to compare the each object with each other and give the result as.

var newCollection =   {name:'user1',phone:'203', rowMatch:'true'},
                      {name:'user2',phone:'5050', rowMatch:'false'},
                      {name:'user1',phone:'203',rowMatch:'true'}

So, I want the new collecition like this where it compares and updates with new property when object properties match like the first and third object.

回答1:

You can use newCollection or manipulate in the collection like this

collection.forEach((item)=>{
item.rowMatch = (collection.filter((e)=>{return (e.name==item.name&&e.phone==item.phone)}).length>1)?'true':'false';
})
console.log(collection)

Simple is that.Here is working JSFiddle for it https://jsfiddle.net/touqeer/pgdsw9Le/1/ .

回答2:

var newCollection = collection.map(item => {
   item.rowMatch = !!collection.find(i => i !== item && i.phone === item.phone && i.name === item.name);
   return item;
});

Here you're just using map to iterate through and check if each item has a duplicate that isn't the original.

回答3:

Create a hash function for your object type.

A simple concatenation of the fields seems to work in this case. Iterate through your collection and for each element, hash it, and put it in a table.

Keep track of the counts. When the count is greater than 1 you know you have a duplicate (row match)

JavaScript Hashmap Equivalent

回答4:

use Array.prototype.find

var newCollection = collection.map((row, index) => {
       if(row["rowMatch"])
          return row; 

      rowMatch = !!collection.find((r,i) => i !== index && r.name === row.name && r.phone === row.phone); 
      row["rowMatch"] = rowMatch;

      return row; 

})

来源：https://stackoverflow.com/questions/47163806/how-to-compare-each-object-in-an-array-with-each-other-when-found-update-the-ob

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javascript

reactjs

underscore.js

lodash