忽略/删除 null，数组计数中未定义和空值 - Javascript

Question

Expected Input:

var arr = [null, 7, 9, undefined, 5, , 0, 8, 2, 1]
console.log(arr.length);

Expected Output:

Length: 7

Answer 1

You can do this way using filter() , it will filter out null and undefined but will keep 0 .

 var array = [null, 7, 9, undefined, 5, , 0, 8, 2, 1]; console.log(array.filter(n=> n == 0 || n ).length)

Answer 2

You can simply use .filter() method and Number.isFinite to get only numbers from array and ignore all falsy values except 0 like this:

 var arr = [null, 7, 9, undefined, 5, , 0, 8, 2, 1] arr = arr.filter(Number.isFinite); console.log(arr);

Answer 3

You could iterate the items and check the value for counting.

 var array = [null, 7, 9, undefined, 5, , 0, 8, 2, 1], length = 0; for (let value of array) if (value;== null && value.== undefined) length++; console.log(length);