Parse document.cookie into object

parsecookie.js

document.cookie.split(';').map(function(c) {
  return c.trim().split('=').map(decodeURIComponent);
}).reduce(function(a, b) {
  try {
    a[b[0]] = JSON.parse(b[1]);
  } catch (e) {
    a[b[0]] = b[1];
  }
  return a;
}, {});

This is good but it does mean iterating over the array twice because you're calling map and then reduce.

I refactored this so it will only iterate once with reduce.

document.cookie.split(';').reduce((cookieObject, cookieString) => {
  let splitCookie = cookieString.split('=').map((cookiePart) => { cookiePart.trim() })
  try {
    cookieObject[splitCookie[0]] = JSON.parse(splitCookie[1])
  } catch (error) {
    cookieObject[splitCookie[0]] = splitCookie[1]
  }
  return cookieObject
})

This way, we split the individual cookies by = and clean them up inside the reducer and save the extra map.

A revision with ES6 syntax.

document.cookie
  .split(';')
  .reduce((res, c) => {
    const [key, val] = c.trim().split('=').map(decodeURIComponent)
    try {
      return Object.assign(res, { [key]: JSON.parse(val) })
    } catch (e) {
      return Object.assign(res, { [key]: val })
    }
  }, {});

and to maintain all number strings as strings (because JSON parses number strings as integers):

document.cookie
  .split(';')
  .reduce((res, c) => {
    const [key, val] = c.trim().split('=').map(decodeURIComponent)
    const allNumbers = str => /^\d+$/.test(str);
    try {
      return Object.assign(res, { [key]: allNumbers(val) ?  val : JSON.parse(val) })
    } catch (e) {
      return Object.assign(res, { [key]: val })
    }
  }, {});

Only this one works for me

let cookie = document.cookie.split(';').reduce((cookieObject, cookieString) => {
   		let splitCookie = cookieString.split('=')
   		try {
   		  cookieObject[splitCookie[0].trim()] = decodeURIComponent(splitCookie[1])
   		} catch (error) {
   			cookieObject[splitCookie[0].trim()] = splitCookie[1]
   		}
   		return cookieObject
   	}, [])

Only this one works for me

let cookie = document.cookie.split(';').reduce((cookieObject, cookieString) => {
   		let splitCookie = cookieString.split('=')
   		try {
   		  cookieObject[splitCookie[0].trim()] = decodeURIComponent(splitCookie[1])
   		} catch (error) {
   			cookieObject[splitCookie[0].trim()] = splitCookie[1]
   		}
   		return cookieObject
   	}, [])

you should be passing in an empty object to reduce instead of an array

Succint

Object.fromEntries(document.cookie.split('; ').map(x => x.split('=')))

It's 2019, and I'm surprised that there's no ES6 construct yet to get directly the cookies as a key->value map. And developers are still required to write their own boilerplate utility methods to parse the cookie string.

Succint

Object.fromEntries(document.cookie.split('; ').map(x => x.split('=')))

That's a beauty one-liner but looking at the cookies at stackoverflow even the cookie values might contain = so based on your solution here's one that takes that into account as well - not a one-liner anymore though but I think my project might just survive with the 3 additional lines

Object.fromEntries(document.cookie.split('; ').map(c => {
    const [ key, ...v ] = c.split('=');
    return [ key, v.join('=') ];
}));

One nit: split(/; */) is more robust than split('; ')

Thanks @benqus, @sz-cgt, I improved it a little more

Object.fromEntries(document.cookie.split(/; */).map(c => {
    const [ key, ...v ] = c.split('=');
    return [ key, decodeURIComponent(v.join('=')) ];
}));

@tail-call returns {"":""} when cookie is empty. It can crash if str is malformed. It splits uselessly.

 document.cookie.split(/; */).reduce((obj, str) => {
	if (str === "") return obj;
	const eq = str.indexOf('=');
	const key = eq > 0 ? str.slice(0, eq) : str;
	let val = eq > 0 ? str.slice(eq + 1) : null;
	if (val != null) try { val = decodeURIComponent(val); } catch(ex) { /* pass */ }
	obj[key] = val;
	return obj;
}, {});

Don't use, see comment below.

Object.fromEntries(document.cookie.split(/; */).map(cookie => cookie.split('=', 2)))

or with decodeURIComponent

Object.fromEntries(document.cookie.split(/; */).map(c => {
    const [ key, v ] = c.split('=', 2);
    return [ key, decodeURIComponent(v) ];
}));

Object.fromEntries(document.cookie.split(/; */).map(cookie => cookie.split('=', 2)))

or with decodeURIComponent

Object.fromEntries(document.cookie.split(/; */).map(c => {
    const [ key, v ] = c.split('=', 2);
    return [ key, decodeURIComponent(v) ];
}));

That's not going to work because if you specify the limit for the String#split() then it'll ignore the remaining after the last split.

const array = "a=b=c".split("=", 2);
// array = ["a", "b"];

Cookie values may contain = as well

@benqus Thanks a lot, I should RTFM. I think I know programming languages where this actually keeps the remaining part but I'm not sure.

.split(/=(.*)$/,2) thats what i did to keep the = at the end

Object.fromEntries(document.cookie.split('; ').map(x => x.split(/=(.*)$/,2).map(decodeURIComponent)))

document.cookie.split("; ").reduce((a,c)=>{let [n,v]=c.split("=");return {...a,[n]:decodeURIComponent(v)};},{})

so these are neat, but does someone have one that's actually been properly tested?

@12Me21 I actually just ran into an issue using the reduce method. Seems that cookies with long values eventually get cut off, leading to obvious issues when you try do something with that value. I've instead opted to use the Object.fromEntries version with no issues so far

I've been using this:

function read_cookies() {
	let cookies = {}
	for (let item of document.cookie.split(";")) {
		let match = item.match(/^\s*([^]*?)="?([^]*?)"?\s*$/)
		if (match)
			cookies[match[1]] = decodeURIComponent(match[2])
	}
	return cookies
}

Rewrite to work on older browsers / js versions:

Object.fromEntries(document.cookie.split(/; */).map(function(c) {
    var index = c.indexOf("=");     // Find the index of the first equal sign
    var key   = c.slice(0, index);  // Everything upto the index is the key
    var value = c.slice(index + 1); // Everything after the index is the value

    // Return the key and value
    return [ decodeURIComponent(key), decodeURIComponent(value) ];
}));

https://stackoverflow.com/a/64472572/8784402

Object.fromEntries(document.cookie.split('; ').map(v=>v.split(/=(.*)/s).map(decodeURIComponent)))