Generate random string/characters in JavaScript
To create a random string in JavaScript, we define a function that generates characters from a predefined set in a loop until the desired string length is met. We utilize Math.random()
for random selection and charAt()
to fetch the character.
This compact solution returns a random alphanumeric string of specified length.
Single-liner for quick random strings
For a quicker solution to generate a 5-character alphanumeric string, you can use this one-liner:
Here, we use toString(36)
to convert the number into a base-36 string, followed by substring()
to trim the string to our desired length.
Crypto for secure random strings
Need higher security? Try crypto.getRandomValues
to generate a cryptographically strong random string.
Noticeably stronger than Math.random()
, this method offers adequate randomness suitable for cryptographic purposes.
Ensuring uniqueness and compatibility
Addressing sequence repetition
Though Math.random()
allows a likelihood of repetitions after ~50K iterations, it is apt for non-critical tasks needing lightweight solutions. But for applications demanding a more robust solution, stronger cryptographic methods are our go-to.
Catering to legacy browsers
While handling legacy browsers like IE11, it is recommended to use (window.crypto || window.msCrypto).getRandomValues
to ensure maximum compatibility. For browser support validation, resources like caniuse.com are a great help.
Achieving unbiased randomness
Given the float-point nature of Math.random()
, distribution is non-uniform, which could introduce bias. This bias is inconsequential for the majority of applications, but for critical applications demanding unbiased randomness, cryptographic tools or third-party string generation libraries are preferred.
Usage tips and optimizations
Array.map() and Array.fill() for code brevity
To adopt a cleaner syntax, you can use Array(N).fill().map()
:
Hexadecimal random strings
Here's how you can generate a random hexadecimal string:
crypto
usage in Node.js
For Node.js environments, make use of crypto.randomBytes
:
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