JS operation Cookie writes and reads instance code

Write a cookie instance!

 
var u = "value=123"; 
document.cookie = u; 

Read the cookie instance, read the value of value!

 
var c_name="value"; //The variable name
if (document.cookie.length > 0) { 
c_start = document.cookie.indexOf(c_name + "=") 
if (c_start != -1) { 
c_start = c_start + c_name.length + 1 
c_end = document.cookie.indexOf(";", c_start) 
if (c_end == -1) c_end = document.cookie.length 
// document.write(document.cookie.substring(c_start,c_end)+"<br>"); 
var sss= unescape(document.cookie.substring(c_start, c_end)) //Take out the values
alert(sss) 
} 
}