subscript/feature/ternary.js

Fast and tiny expression evaluator with minimal syntax.

import { token, expr, next } from '../src/parse.js'
import { operator, compile } from '../src/compile.js'
import { PREC_ASSIGN, COLON } from '../src/const.js'

// ?:
// token('?', PREC_ASSIGN, (a, b, c) => a && (b = expr(PREC_ASSIGN - 1, COLON)) && (c = expr(PREC_ASSIGN - 1), ['?', a, b, c]))
// ALT: not throwing
token('?', PREC_ASSIGN, (a, b, c) => a && (b = expr(PREC_ASSIGN - 1)) && next(c => c === COLON) && (c = expr(PREC_ASSIGN - 1), ['?', a, b, c]))

operator('?', (a, b, c) => (a = compile(a), b = compile(b), c = compile(c), ctx => a(ctx) ? b(ctx) : c(ctx)))