JS 数组各元素之积

let arr = [1, 9, 3, 4, 5, 6];

methods1:

 function multiply1(arrary) {
        if (arrary instanceof Array) {
            let result = arrary.length > 0 ? 1 : null;
            if (arrary.indexOf(0) > 0) {
                return result = 0;
                
            }
            for (let i = 0; i < arrary.length; i++) {
                result *= arrary[i];
            }
            return result;
        }
        return null;
    }
  console.log(multiply(arr));

methods2:

function multiply2(arrary) {
      if (arrary instanceof Array){
            return arrary.reduce(function(a,b){
                return a*b;
            }) 
       }
 }
  console.log(multiply2(arr));