Use js to read, write and delete cookie code sharing and detailed comments_javascript skills

//Verified
// JavaScript Document
//Instructions for use:
//Set cache: setCookie("name",value);
//Get cache: var name=getCookie("name");
//Delete cache ：delCookie("name");
///Set cookie
function setCookie(NameOfCookie, value, expiredays)
{
//@Parameters: Three variables are used to set new cookies:
//The name of the cookie, the stored cookie value,
// and the cookie expiration time.
// These lines convert the number of days into a legal date
var ExpireDate = new Date ( );
ExpireDate.setTime(ExpireDate.getTime() (expiredays * 24 * 3600 * 1000));
// The following line is used to store cookies, just simply "document.cookie" Just assign a value.
// Note that the date is converted into GMT time through the toGMTstring() function.
document.cookie = NameOfCookie "=" escape(value) ((expiredays == null) ? "" : "; expires=" ExpireDate.toGMTString());
}
///Get cookie Value
function getCookie(NameOfCookie)
{
// First we check whether the cookie exists.
// If it does not exist, the length of document.cookie is 0
if (document.cookie .length > 0)
{
// Then we check whether the cookie name exists in document.cookie
// Because more than one cookie value is stored, even if the length of document.cookie is not 0 There is no guarantee that the cookie with the name we want exists
//So we need this step to see if there is a cookie we want
//If the variable value of begin is -1, it means it does not exist
begin = document.cookie.indexOf(NameOfCookie "=");
if (begin != -1)
{
// Indicates the existence of our cookie.
begin = NameOfCookie.length 1;//Initial position of cookie value
end = document.cookie.indexOf(";", begin);//End position
if (end == -1) end = document.cookie.length; //No; then end is the end position of the string
return unescape(document.cookie.substring(begin, end));
}
}
return null;
// cookie is not Returns null
}
///Delete cookie
function delCookie (NameOfCookie)
{
// This function checks whether the cookie is set, and if it is set, the expiration time is moved to the past time;
//The rest is left to the operating system to clear the cookie at the appropriate time
if (getCookie(NameOfCookie))
{
document.cookie = NameOfCookie "=" "; expires=Thu , 01-Jan-70 00:00:01 GMT";
}
}