return statement javascript

<script>
function showName() {
  var result;
  result = addString('Hello', ' World');
  document.write (result );
}

// in below we will check how to return string from function
function addString(fName, lName) {
  var val;
  val = fName + lName;
  return val;  // returning string from function
}
</script>
<input type = "button" onclick = "showName()" value = "Result">
  
/*
I hope it will help you.
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*/function test(arg){
    return arg;
}function add(a, b) {
  return a + b; //Return stops the execution of this function
}

var sum = add(5, 24); //The value that was returned got but inside the variable sum