JSPM

/\bconst\s+/g

const x = 12;
// const y = 13;
let z = "const ";

import { grub } from "@digitak/grubber";

const content = `
const x = 12
// const y = 13
let z = "const "
`;

const results = grub(content).find(/\bconst\s+/);
console.log(results.length);  // will print 1 as expected

export function grub(
  source: string,
  languageOrRules: LanguageName | Rule[] = "es"
): {
  // find one or more expressions and return an array of fragments
  find: (...expressions: Array<string | RegExp>) => Fragment[],

  // replace one or more expressions and return the patched string
  replace: (...fromTos: Array<{
    from: string | RegExp,
    to: string | RegExp
  }>) => string,

  // find all dependencies (ex: `imports` in Typescript, `use` in Rust)
  findDependencies: () => Fragment[],

  // replace all dependencies by the given value
  // you can use special replace patterns like "$1" to replace
  // with the first captured group
  replaceDependencies: (to: string) => string,
}

export type Fragment = {
  slice: string // the matched substring
  start: number // start of the matched substring
  end: number // end of the matched substring
  groups: string[] = [] // the captured groups
};

export type LanguageName =
  | 'es' // Ecmascript (Javascript / Typescript / Haxe): the default
  | 'rs' // Rust
  | 'css'
  | 'scss'
  | 'sass'
  | 'c'
  | 'cpp'
  | 'py' // Python
  | 'nim'
  ;

// find all semi-colons inside the rust source code
grub(rustCodeToParse, "rs").find(";");

export type Rule =
  |  {
      expression: string | RegExp // the expression to ignore

      // if returns false, the match is ignored
      onExpressionMatch?: (match: RegExpMatchArray) => boolean | void
    }
  |  {
      startAt: string | RegExp // start of the expression to ignore
      stopAt: string | RegExp // stop of the expression to ignore

      // if returns false, the match is ignored
      onStartMatch?: (match: RegExpMatchArray) => boolean | void
      onStopMatch?: (match: RegExpMatchArray) => boolean | void
    }
  ;

const rules: Rule[] = [
  {
    // string
    expression: /".*?[^\\](?:\\\\)*"/,
  },
  {
    // single line comment
    expression: /\/\/.*/,
  },
  {
    // multiline comment
    expression: /\/\*((?:.|\s)*?)\*\//,
  },
];