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Selected Reading
What is the shortest function of reading a cookie by name in JavaScript?
The shortest way to read a cookie by name in JavaScript is using a one-line function that searches through document.cookie and extracts the specific value.
Shortest Cookie Reader Function
Here's the most concise function to read a cookie by name:
<html>
<head>
<title>Cookie Reader</title>
</head>
<body>
<script>
// Set some cookies first for testing
document.cookie = "username=john; path=/";
document.cookie = "theme=dark; path=/";
document.cookie = "language=en; path=/";
// Shortest function to read cookie by name
function getCookie(name) {
return document.cookie.split('; ').find(row => row.startsWith(name + '='))?.split('=')[1];
}
// Test the function
console.log("Username:", getCookie("username"));
console.log("Theme:", getCookie("theme"));
console.log("Language:", getCookie("language"));
console.log("Nonexistent:", getCookie("nonexistent"));
</script>
</body>
</html>
Username: john Theme: dark Language: en Nonexistent: undefined
How It Works
The function works by:
- Splitting
document.cookieby'; 'to get individual cookie pairs - Using
find()to locate the cookie that starts with the given name - Using optional chaining
?.to handle cases where the cookie doesn't exist - Splitting by
'='and returning the value part
Alternative Approaches
Here are other common methods for comparison:
<html>
<head>
<title>Cookie Reading Methods</title>
</head>
<body>
<script>
// Set test cookies
document.cookie = "user=alice; path=/";
document.cookie = "role=admin; path=/";
// Method 1: Using regular expression
function getCookieRegex(name) {
const match = document.cookie.match(new RegExp('(^| )' + name + '=([^;]+)'));
return match ? match[2] : null;
}
// Method 2: Traditional loop approach
function getCookieLoop(name) {
const cookies = document.cookie.split(';');
for (let i = 0; i < cookies.length; i++) {
let cookie = cookies[i].trim();
if (cookie.indexOf(name + '=') === 0) {
return cookie.substring(name.length + 1);
}
}
return null;
}
console.log("Regex method:", getCookieRegex("user"));
console.log("Loop method:", getCookieLoop("role"));
</script>
</body>
</html>
Regex method: alice Loop method: admin
Comparison
| Method | Code Length | Performance | Browser Support |
|---|---|---|---|
| Modern (find + optional chaining) | Shortest | Good | ES2020+ |
| Regular Expression | Medium | Good | All browsers |
| Traditional Loop | Longest | Best | All browsers |
Complete Example with Error Handling
<html>
<head>
<title>Robust Cookie Reader</title>
</head>
<body>
<script>
// Enhanced version with better error handling
function getCookie(name) {
if (!name || !document.cookie) return null;
const cookie = document.cookie
.split('; ')
.find(row => row.startsWith(name + '='));
return cookie ? decodeURIComponent(cookie.split('=')[1]) : null;
}
// Set a cookie with encoded value
document.cookie = "message=" + encodeURIComponent("Hello World!") + "; path=/";
console.log("Decoded message:", getCookie("message"));
console.log("Missing cookie:", getCookie("missing"));
</script>
</body>
</html>
Decoded message: Hello World! Missing cookie: null
Conclusion
The shortest cookie reader uses modern JavaScript features like find() and optional chaining. For maximum browser compatibility, use the traditional loop or regex approach.
Updated on: 2026-03-15T23:18:59+05:30
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