clean_an_array.js

let k = {
  x: ['mi', 'ko'],
	y: []
}
function clean(obj) {
  for (let propName in obj) { 
    if (obj.hasOwnProperty(propName)) {
      if (!obj[propName].length) {
        delete obj[propName];
      }
    }
  }
}
console.log(clean(k))
console.log(k)