/**
 * 
 * @param {Array} arr1 
 * @param {Array} arr2 
 */
export function difference(arr1, arr2=[]){
 //判断参数
 if(arr1.length === 0){
 return [];
 }
 if(arr2.length === 0){
 return arr1.slice();
 }
 const result = arr1.filter(item => !arr2.includes(item));
 return result;
}