Calculate the entropy of a password string, but fast!
npm install fast-password-entropy
 
Calculate the entropy bits of a string as a quick proxy to password strength.
See Entropy as a measure of password strength for more information.
``bash`
$ npm install --save fast-password-entropy
`js
const stringEntropy = require('fast-password-entropy')
console.log(stringEntropy('1234')) // 13
console.log(stringEntropy('password')) // 38
`
A transpiled version is available in es5/index.js. To use that specific version, this syntax is also supported:
`js`
var stringEntropy = require('fast-password-entropy/es5');
Several libraries were analyzed before creating this one. Some of those are listed below, along with the drawbacks found for each one.
information-entropy: Too basic. Cannot extract charset length from the string being tested.
joi-password-complexity: Interesting but not providing raw entropy information.
passwd-strength: Values are correct but is too slow.
password-entropy: Entropy calculation is not following any standard so results are very different from other libs.
password-strength: Only giving "simple", "medium", "strong" values.
string-entropy: Provides good entropy values but is slow.
tai-password-strength: Very complex and results are not fully matching the expected results.
zxcvbn: Uses comprehensive heuristics to estimate complexity but solves a much more complex problem instead.
After the research, only three libraries were analyzed in detail and benchmarked. This library results are 3.5x faster than the existing libraries.
`
$ npm run bench
Test strings [ '',
'8646',
'xtcmFWoH',
'Lp2x0P1iMEPWZKaQ',
'escape piece useful cloth',
'needle excitement over aloud price among',
'topic contain anything political great thank dawn among butter doll fought end' ]
Results for fast-password-entropy [ 0, 13, 46, 95, 147, 235, 459 ]passwd-strength
Results for [ 0, 13, 46, 95, 147, 235, 459 ]password-entropy
Results for [ 1, 1, 3, 10, 10, 10, 10 ]string-entropy
Results for [ 0, 13, 46, 95, 118, 188, 367 ]tai-password-strength
Results for [ 0, 6, 24, 62, 87, 152, 312 ]
Benchmarking...
fast-password-entropy x 557,198 ops/sec ±1.27% (87 runs sampled)
passwd-strength x 1,732 ops/sec ±4.36% (81 runs sampled)
string-entropy x 143,412 ops/sec ±3.92% (83 runs sampled)
tai-password-strength x 11,590 ops/sec ±1.28% (86 runs sampled)
Fastest is fast-password-entropy
``
MIT