read cookie in browser javascript code example

Example 1: javascript create cookie

function setCookie(name,value,days) {
    var expires = "";
    if (days) {
        var date = new Date();
        date.setTime(date.getTime() + (days*24*60*60*1000));
        expires = "; expires=" + date.toUTCString();
    }
    document.cookie = name + "=" + (value || "")  + expires + "; path=/";
}
function getCookie(name) {
    var nameEQ = name + "=";
    var ca = document.cookie.split(';');
    for(var i=0;i < ca.length;i++) {
        var c = ca[i];
        while (c.charAt(0)==' ') c = c.substring(1,c.length);
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
    }
    return null;
}

setCookie("user_email","[email protected]",30); //set "user_email" cookie, expires in 30 days
var userEmail=getCookie("user_email");//"[email protected]"

Example 2: get cookie value in javascript

const getCookie = (cookie_name) =>{
  // Construct a RegExp object as to include the variable name
  const re = new RegExp(`(?<=${cookie_name}=)[^;]*`);
  try{
    return document.cookie.match(re)[0];	// Will raise TypeError if cookie is not found
  }catch{
    return "this-cookie-doesn't-exist";
  }
}

getCookie('csrftoken')	// ADZlxZaPSa6k4oyelVBa5iWTtLJW8P3Jf7nhW90L2ZWc5Zcq2vKLO1RRFbaKco3C
getCookie('_non_existent') // this-cookie-doesn't-exist