Aprils
Aprils is a little library for quickly writing parsers from scratch
Here's simple parser for words.
const { match, peek, feed } = require('aprils')
function letters() {
return match(/^\w+/)
}
function separator() {
return match(/^\W*/) // stuff like spaces and periods
}
function word() {
sparator()
return letters()
}Let's test it out!
feed('Luke, I am your father')
word() // returns 'Luke'
word() // returns 'I'"
word() // returns 'am'Use peek to check the next token
function upper() {
return match(/^[A-Z]/)
}
function lower() {
return match(/^[a-z]/)
}
feed("AbCdE")
peek(upper) // returns `true` because the next token is uppercase
peek(lower) // returns `false` because the next token isn't lowercaseUse skip to add choices
const { skip } = require('aprils')
// match lowercase or uppercase
function letter() {
return skip(lower) || upper()
}
feed('AbC')
letter() // returns 'A'
letter() // returns 'b'
letter() // returns 'C'You can add more choices using JavaScript's || operator
// accept A or B or ... or Z
skip(A) || skip(B) || ... || skip(Y) || Z()API
feed(string)
Sets the input string.
match(pattern)
Consumes and returns part of the input string that matches pattern. Note that pattern should start with ^ to match from the start of the input string.
peek(parser, [args...])
Executes a parser and returns true if it was successful. The input string isn't consumed.
skip(parser, [args...])
Executes a parser and returns the result if it was successful. The input string is only consumed on success.