数组中的javascript过滤器数组

Question

I have the following code based on docs

var arr = [
  { id: 15 },
  { x: [{ id: 777 }, { id: 'xx' }, { notidproperty: 987 }]},
  { id: 1111 }
];

function filterByID(obj) {
  if ('id' in obj && typeof(obj.id) === 'number' && !isNaN(obj.id)) {
    return true;
  } else if (Object.prototype.toString.call(obj) === '[object Array]') { //obj type is Object, not Array
    obj.filter(filterByID);
  } else {
    return false;
  }
}

var arrByID = arr.filter(filterByID);
console.log('expected length = 3, actual length = ' + arrByID.length);
console.log(arrByID);

How can I filter 'arr' array ? Is there any other techniques to get proper result?

EDIT: the expected result is filtered array of objects that have id property with numeric value

So expected Id values are 15, 777, 1111

Answer 1

I suggest to use Array#reduce() instead of Array#filter() , because you need a flat array for the result, to count.

I use isFinite as check for the id .

 function rr(r, a) { Object.keys(a).forEach(function (k) { if (Array.isArray(a[k])) { r = r.concat(a[k].reduce(rr, [])); } else { isFinite(a.id) && r.push(a); } }); return r; } var arr = [{ id: 15 }, { x: [{ id: 777 }, { id: 'xx' }, { notidproperty: 987 }] }, { id: 1111 }], result = arr.reduce(rr, []); document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

Answer 2

Almost there. In the else if you don't return anything. Instead of

obj.filter(filterByID);

try return (obj.filter(filterByID).length > 0);

because if the result of the recursive filterByID is an array with length more than 0, you want to add that to the outer result.

Answer 3

You have to modify the following branch:

if (Object.prototype.toString.call(obj) === '[object Array]') { //obj type is Object, not Array
  obj.filter(filterByID);
}

This only filters but returns no result. And your object with x property of Array type will not be processed here. So:

if(obj.x && Array.isArray(obj.x)){
  return obj.x.filter(filterByID).length>0
}

Or:

if(obj.x && Array.isArray(obj.x)){
  obj.x = obj.x.filter(filterByID)
  return true
}

(Depending on what you want to do)