Function intersection

Takes a sequence of regular expressions and constructs their intersection. This is useful to combine several constraints into one. For example, to build a regular expression that can validate a new password:

import { intersection } from '@gruhn/regex-utils'

const passwordRegex = intersection(
  /.{12,}/, // 12 letters or more
  /[0-9]/,  // at least one number
  /[A-Z]/,  // at least one upper case letter   
  /[a-z]/,  // at least one lower case letter
)

function isValidPassword(str: string) {
  return passwordRegex.test(str)
}
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In most cases it's simpler and more efficient to match each RegExp individually:

function isValidPassword(str: string) {
  return /.{12,}/.test(str) && /[0-9]/.test(str) && /[A-Z]/.test(str) && /[a-z]/.test(str)
}
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However, this is not always possible. For example, when a third-party interface expect a single RegExp as input like:

• Express.js - for route parameter matching and path specifications
• Yup/Joi/Zod - for string pattern validation
• Webpack - in various configuration options like test, include, and exclude patterns
• fast-check - for random string generation during fuzzing / property based testing