blurstparser.js

const TOKENS = {
  id: /[a-z]+/,
  num: /(?:[0-9]+\.)?[0-9]+/,
  op: /[+-/*]/,
  leftparen: /\(/,
  rightparen: /\)/,
  error: /./
}

function* tokenize(str, tokens) {
  const names = Object.keys(tokens)
  const pattern = Object.values(tokens).map(x => `(${x.source})`).join('|')
  const re = new RegExp(pattern, 'g')

  let match;
  while (match = re.exec(str)) {
    for (let i = 1; i < match.length; i++) {
      if (match[i] !== undefined) {
        yield {type: names[i-1], content: match[i], index: match.index}
        break
      }
    }
  }
}

for (const token of tokenize('-123+abc(456.78*9)', TOKENS)) {
  console.log(token)
}