To determine the length of a string, that is, to determine how many characters the string currently contains, look at the "length" property of the string.
Code:
<script type="text/javascript">
//<![CDATA[
my_string = "A Historic Inauguration";
document.write("The length of \"", my_string, "\" is : ", my_string.length);
//]]>
</script>
Output: