let a = [1, 2, 3, 4]
    console.log(a)
 
    let b = [2, 4, 5]
 
    let aSet = new Set(a)
    let bSet = new Set(b)
    
    // 并集
    let union = Array.from(new Set(a.concat(b))) // [1,2,3,4,5]
    console.log(union)
    
    // 交集
    let intersection = Array.from(new Set(a.filter(v => bSet.has(v))))// [2,4]
    
    
    // 差集
    let diff = Array.from(new Set(a.concat(b).filter(v => aSet.has(v) && !bSet.has(v)))  
    )//[1,3]
    console.log(diff)
//找出两个数组并集
function getUnion(arr1, arr2) {
    let aSet = new Set(arr1);
    let bSet = new Set(arr2);
    
    // 并集
    let union = Array.from(new Set(arr1.concat(arr2)));
    return union;
}
//找出两个数组的差集
function getDiff(arr1, arr2) {
    let aSet = new Set(arr1);
    let bSet = new Set(arr2);
    
    // 并集
    let diff = Array.from(
            new Set(arr1.concat(arr2).filter(v => aSet.has(v) && !bSet.has(v)))  
    );
    return diff;
}
//找出两个数组的交集
function getInter(arr1, arr2) {
    let aSet = new Set(arr1);
    let bSet = new Set(arr2);
    
    let inter = Array.from(new Set(aSet.filter(v => bSet.has(v))));
    return inter;
}