let arr1 = ['a','b','c','d'];
let arr2 = [1,4];
arr1.filter((value,index)=>{
    return arr2.indexOf(index) === -1;
});

arr1.filter(function(){
       for(let i = 0 , i < arr2.length, i++){
              return arr1[arr2[i]] 
       }
})

let newArr = arr1.filter((el, index, array) => {
    return arr2.indexOf(index) === -1
})

let newArr = arr1.filter((el, index, array) => {
    return !arr2.includes(index)
})

arr1 = arr1.filter((e,i) => arr2.indexOf(i)===-1)
下标从0开始