compare two array of objects javascript and throw the unmatched array elements into new array using underscore or lodash [closed]

问题

I have two arrays apple = [1,5,10,15,20], bottle = [1,5,10,15,20,25] using lodash or any javascript function, I want an array c with unique elements c= [25]. To be more precise, I want the list of all the elements when 'apple' array is compared with 'bottle' array, to display the elements which are unique/

回答1:

You could use Array#filter with a Set of the opposite array.

This proposal uses a complement function which returns true if the element a is not in the set b.

For a symmetric difference, the filtering with callback has to be used for both sides.

function getComplement(collection) {
    // initialize and close over a set created from the collection passed in
    var set = new Set(collection);
    // return iterator callback for .filter()
    return function (item) {
        return !set.has(item);
    };
}
var apple = [1,5,10,15,20], 
    bottle = [1,5,10,15,20,25],
    unique = [
        ...apple.filter(getComplement(bottle)),
        ...bottle.filter(getComplement(apple))
    ];

console.log(unique);

回答2:

You can create your own function with reduce() and filter() for this.

var apple = [1,5,10,15,20], bottle = [1,5,10,15,20,25] 

function diff(a1, a2) {
  //Concat array2 to array1 to create one array, and then use reduce on that array to return
  //one object as result where key is element and value is number of occurrences of that element
  var obj = a1.concat(a2).reduce(function(result, element) {
    result[element] = (result[element] || 0) + 1
    return result
  }, {})
  
  //Then as function result return keys from previous object where value is == 1 which means that
  // that element is unique in both arrays.
  return Object.keys(obj).filter(function(element) {
    return obj[element] == 1
  })
}

console.log(diff(apple, bottle))

Shorter version of same code with ES6 arrow functions.

var apple = [1,5,10,15,20], bottle = [1,5,10,15,20,25] 

function diff(a1, a2) {
  var obj = a1.concat(a2).reduce((r, e) => (r[e] = (r[e] || 0) + 1, r), {})
  return Object.keys(obj).filter(e => obj[e] == 1)
}

console.log(diff(apple, bottle))

来源：https://stackoverflow.com/questions/42496158/compare-two-array-of-objects-javascript-and-throw-the-unmatched-array-elements-i

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