比较两个数组，并用第三个数组中的值替换重复项

Question

var array1 = ['a','b','c','d'];
var array2 = ['a','v','n','d','i','f'];

var array3 = ['1','2','3','4','5','6'];

Just starting to learn Javascript, I can't figure out how to compare the values of array2 to those on array1 and if so replace it with the corresponded array index from array3 .

To turn it like this:

array2 = ['1','v','n','4','i','f'];

But also, it has to compare the values from array1 and array2 even if the index positions are different like this:

var array1 = ['a','b','c','d'];
var array2 = ['d','v','n','a','i','f'];

Thanks for the help

Answer 1

Use Array.prototype.reduce to check the duplicates and create a new array - see demo below:

 var array1 = ['a','b','c','d']; var array2 = ['a','v','n','d','i','f']; var array3 = ['1','2','3','4','5','6']; var result = array2.reduce(function(p,c,i){ if(array1.indexOf(c) !== -1) { p.push(array3[i]); } else { p.push(c); } return p; },[]); console.log(result); 

Answer 2

You can use map() on array2 and see if current element is same as element in array1 with same index if it is return element from array3 with index of i else return current element or e

 var array1 = ['a', 'b', 'c', 'd']; var array2 = ['a', 'v', 'n', 'd', 'i', 'f']; var array3 = ['1', '2', '3', '4', '5', '6']; var result = array2.map(function(e, i) { return e == array1[i] ? array3[i] : e; }) console.log(result) 

Answer 3

使用Array＃map

array2.map((v, i) => v === array1[i] ? array3[i] : v);

Answer 4

there are many forms, this is a basic form:

var array1 = ['a','b','c','d'];
var array2 = ['a','v','n','d','i','f'];
var array3 = ['1','2','3','4','5','6'];
var result = [];//define array of result
for(var i=0;i<array2.length;i++){//Iterate the array2
    if(array2[i] == array1[i])//Compare if array1 in index 'i' with array2 in index 'i'
        result[i] = array3[i];//if true put in result in index 'i' from array3
    else
        result[i] = array2[i];//else put in result in index 'i' from array2
}
console.log(result);//show in console the result

Answer 5

Here you have some code that does what you ask:

    var array1 = ['a','b','c','d'];
    var array2 = ['a','v','n','d','i','f'];
    var array3 = ['1','2','3','4','5','6'];
    var biggerArrayLength = 0;

        if(array1.length > array2.length){
            biggerArrayLength = array1.length;
        }else{
            biggerArrayLength = array2.length;
        }

        for(var i = 0; i < biggerArrayLength; i++){
            if(array1[i] == array2[i]){
                array2[i] = array3[i];
            }
        }

Hope it helps!

Answer 6

You could use a hash table and check against. If the string is not included in the hash table, a replacement value is set for this element.

 var array1 = ['a','b','c','d'], array2 = ['d','v','n','a','i','f'], array3 = ['1','2','3','4','5','6'], hash = Object.create(null); array1.forEach(function (a) { hash[a] = true; }); array2.forEach(function (a, i, aa) { if (hash[a]) { aa[i] = array3[i]; } }); console.log(array2); 

ES6 with Set

 var array1 = ['a','b','c','d'], array2 = ['d','v','n','a','i','f'], array3 = ['1','2','3','4','5','6']; array2.forEach((hash => (a, i, aa) => { if (hash.has(a)) { aa[i] = array3[i]; } })(new Set(array1))); console.log(array2); 

Answer 7

function replaceDuplicates(array1, array2, array3) {

    // array3 can't be smaller than array1!
    if (array3.length < array1.length) throw new Error('array3 < array1');

    // Loop through all the items in array1...
    for (var i = 0; i < array1.length; i++) {

        // Check if the item in array2 matches...
        if (i < array2.length && array2[i] === array1[i]) {

            // And if it does replace array1's item with array3's item!
            array1[i] = array3[i];

        }
    }
}


var array1 = ['a','b','c','d'];
var array2 = ['a','v','n','d','i','f'];
var array3 = ['1','2','3','4','5','6'];

replaceDuplicates(array1, array2, array3);

console.log(array1); // ['1','v','n','4','i','f']