It's easy in Javascript to know how many characters are in string using the property .length.
// Juste use the property .length
var size = 'Our lovely string'.length;Note: Strings can not be substracted, multiplied or divided.
Store in the variable named size the length of str.
var str = "Hello World";
var size = var str = "Hello World";
var size = str.length;assert(size == str.length);