ifless

Conditional logic expressed using natural-language operators via JavaScript template literals.

Why? An experimental project for fun and learning, exploring alternative syntax for conditional logic.

Examples

• CodeSandbox (check console output)
• Local examples
• Unit tests
• Integration tests
• Tests with JS eval() as comparator

Usage

npm install ifless and use as follows:

import { when } from '@twistezo/ifless'
// or const { when } = require('@twistezo/ifless')

const user = { active: true }
const isAdmin = false

// classic
if (user.active && !isAdmin) {
  console.log('condition met')
}

// with 'when'
when`${user.active} AND NOT ${isAdmin}`(() => {
  console.log('condition met')
})

// with context and aliases
when.ctx({
  admin: isAdmin,
  userActive: user.active,
})`#userActive AND NOT #admin`(() => {
  console.log('condition met')
})

// complex example
when.ctx({
  a: true,
  b: false,
  c: false,
})`(#a AND #b) OR (NOT #c AND ${true})`(() => {
  console.log('condition met')
})

Limitations

Accepted:

• ${value}
• #alias
• operators AND, OR, NOT
• parentheses (, )

Not accepted:

• other words
• empty parentheses
• double negations NOT NOT, !!${value}, #{!!value}
• aliases without value in context
• functions in context

Features

• AND, &&

  • Before:

    if (a && b)

  • After:

    when.ctx({ a, b })`#a AND #b`(() => {})

• OR, ||

  • Before:

    if (a || b)

  • After:

    when.ctx({ a, b })`#a OR #b`(() => {})

• NOT, !

  • Before:

    if (!a)

  • After:

    when.ctx({ a })`NOT #a`(() => {})

• Parentheses

  • Before:

    if ((a && b) || (!c && (d || e)))

  • After:

    when.ctx({ a, b, c, d, e })`(#a AND #b) OR (NOT #c AND (#d OR #e))`(() => {})

• Short-circuit evaluation

  • Before:

    if (a && expensiveCheck())

  • After:

    when`${a} AND ${() => expensiveCheck()}`(() => {})

• Double negation !!

  • Before:

    if (!!a && !!b)

  • After:

    when.ctx({ a, b })`#a AND #b`(() => {})

• null/undefined as false

  • Before:

    if (a != undefiend && b != null)

  • After:

    when.ctx({ a, b })`#a AND #b`(() => {})

Development

bun run example     # run examples
bun run build       # build all formats

bun run test        # run all tests
bun run lint        # check lint
bun run lint:fix    # fix lint & format
bun run typecheck   # check types

bunx npm login      # login to npm
bun publish         # publish to npm