let a_list = [
  {
    desc: 'Hello World'
  },
  {
    desc: 'Second Item'
  },
  {
    desc: 'third'
  }
]

let total_count = 0

calcArrayStringLengths(array, property, set_value) {
  let counts = []
  array.forEach(i => {
    counts.push(i[property].length)
  })
  this[set_value] = counts.reduce((accumulator, currentValue) =>  accumulator + currentValue) // for VueJs
  //or
  total_count = counts.reduce((accumulator, currentValue) =>  accumulator + currentValue) // for VueJs
}

calcArrayStringLengths(a_list, desc, total_count)