tokenize.js

let RegExpObject = /(-?[0-9]+)|(\+)|(\*)|(\-)|(\/)|(\()|(\))/g;
const tokenTypes = require("./tokenTypes");
const TokenReader = require("./tokenReader");
const tokenNames = [
  tokenTypes.Number,
  tokenTypes.Plus,
  tokenTypes.Multiply,
  tokenTypes.Minus,
  tokenTypes.Divide,
  tokenTypes.LeftPara,
  tokenTypes.RightPara,
];

function* tokenizer(script) {
  let result;
  while (true) {
    result = RegExpObject.exec(script);
    if (!result) {
      break;
    }
    let index = result.findIndex((item, index) => index > 0 && !!item);
    let token = { type: tokenNames[index - 1], value: result[0] };
    yield token;
  }
}
function tokenize(script) {
  const tokens = [];
  for (let token of tokenizer(script)) {
    tokens.push(token);
  }
  return new TokenReader(tokens);
}

module.exports = tokenize;