比較兩個對象的數組javascript並將不匹配的數組元素使用下劃線或lodash

Question

我有兩個數組apple = [1,5,10,15,20]，bottle = [1,5,10,15,20,25]使用lodash或任何JavaScript函數，我想要一個數組c與唯一元素c= [25]。更確切地說，當'apple'數組與'bottle'數組進行比較時，我需要所有元素的列表，以顯示唯一的元素/

Answer 1

您可以使用reduce()和filter()創建您自己的函數。

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))

較短的版本與ES6箭頭功能相同的代碼。

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))

Answer 2

你可以使用Array#filter與對面陣列的Set。

該建議使用complement函數，如果元素a不在集合b中，則返回true。

對於對稱差異，必須在雙方都使用回調過濾。

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);