Javascript Program for Maximize elements using another array

// Javascript program to print the maximum elements
// giving second array higher priority

// Function to maximize array elements
function maximizeArray(arr1, arr2) {

    // auxiliary array arr3 to store 
    // elements of arr1 & arr2
    let arr3 = new Array(10);
    for (let i = 0; i < arr3.length; i++) {
        // arr2 has high priority
        arr3[i] = 0;
    }

    // Arraylist to store n largest
    // unique elements
    let al = [];

    for (let i = 0; i < arr2.length; i++) {
        if (arr3[arr2[i]] == 0) {

            // to avoid repetition of digits of arr2 in arr3
            arr3[arr2[i]] = 2;

            // simultaneously setting arraylist to 
            // preserve order of arr2 and arr3
            al.push(arr2[i]);
        }
    }

    for (let i = 0; i < arr1.length; i++) {
        if (arr3[arr1[i]] == 0) {

            // if digit is already present in arr2
            // then priority is arr2
            arr3[arr1[i]] = 1;

            // simultaneously setting arraylist to
            // preserve order of arr1
            al.push(arr1[i]);
        }
    }

    // to get only highest n elements(arr2+arr1)
    // and remove others from arraylist
    let count = 0;
    for (let j = 9; j >= 0; j--) {
        if (count < arr1.length &
            (arr3[j] == 2 || arr3[j] == 1)) {

            // to not allow those elements 
            // which are absent in both arrays
            count++;
        }
        else {

            if (al.indexOf(j) > 0)
                al.splice(al.indexOf(j), 1);

        }
    }

    let i = 0;
    for (let x = 0; x < al.length; x++) {
        arr1[i++] = al[x];
    }

}

// Driver Code
let arr1 = [7, 4, 8, 0, 1];
let arr2 = [9, 7, 2, 3, 6];
maximizeArray(arr1, arr2);
console.log(arr1);