example.ts

const arrayOfStrings: string[] = [];
arrayOfStrings.push('hello');
arrayOfStrings.push('world');
arrayOfStrings.push('how are');
arrayOfStrings.push('you');

let charCounter = 0;
for (let i = 0; i < arrayOfStrings.length; i ++) {
   for (let k = 0; k < arrayOfStrings[i].length; k++) {
       charCounter++;
   }
}
console.log(charCounter);