JavaScript uses a regular fetch cookie

application uses regular expressions to get cookies

cookie = "id=123; Username=yang; id=123; Sex=1 "
If you want to get an ID now, how to write the regular expression.
The method of representing the value ([^;] *) Repeat any number of characters except the semicolon
The judgment of the end symbol (; |$)
var cookie = "id=123; Username=yang; Sex=1 ";
var reg4 =/(^|) Id= ([^;] *) (; |$)/;//a regular that matches a cookie
var arr = Cookie.match (REG4);//match method plays an array
Console.log (arr[2]);


Gets the Usernama corresponding value
var reg5 =/(^|) Username= ([^;] *) (; |$)/;//Gets the value of username
var arr2 = Cookie.match (REG5);
Console.log (ARR2); If the match method is not found, it returns null ["Username=yang;", "", "Yang", ";", Index:7, Input: "id=123; Username=yang; Sex=1 "]
Console.log (arr2[2]);//The second in the array is the value of the second group.


Gets the cookie corresponding to a cookie
function GetCookie (key) {
var str = "(^|)" + key + "= ([^;]) (;|$)";//[,,,]
var reg = new RegExp (str);
if (!arr)//arr array is null match did not find the cookie in the string
{
return null;
}
Return arr[2];//only need the value indexed in the array to be 2
}
Document.cookie = "Username=yang;";
Document.cookie = "id=123";


Alert (GetCookie ("color"));
Alert (GetCookie ("username"));