org.eclipse.scout.rt.ui.html/src/main/js/scout/form/fields/numberfield/Calculator.js

/*******************************************************************************
 * Copyright (c) 2014-2015 BSI Business Systems Integration AG.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     BSI Business Systems Integration AG - initial API and implementation
 ******************************************************************************/
/*
 * A simple calculator similar to eval but safe in use.
 * Supports the following format:
 * group character ( )
 * digits 0-9
 * operators + - * /
 * decimal separator .
 * no grouping character
 * no whitespace
 */
scout.Calculator = function() {};

scout.Calculator.prototype.isFormula = function(input) {
  return input.match(/^[\d\(\)\+\-\*\/\.]+$/);
};

scout.Calculator.prototype.evalFormula = function(input) {
  this._tokens = input
    .split(/([\d.]+|\(|\)|[\+\-\*\/])/)
    .filter(function(e) {
      return e.length !== 0;
    });
  return this._expr();
};

scout.Calculator.prototype._next = function() {
  if (this._tokens.length === 0) {
    return undefined;
  }
  return this._tokens[0];
};

scout.Calculator.prototype._consumeNext = function() {
  var cur = this._tokens[0];
  this._tokens = this._tokens.slice(1, this._tokens.length);
  return cur;
};

scout.Calculator.prototype._expr = function() {
  return this._sum();
};

//a+b+...
scout.Calculator.prototype._sum = function() {
  var v = this._prod();
  while (this._next() === '+' || this._next() === '-') {
    switch (this._consumeNext()) { // NOSONAR
      case '+':
        v = v + this._prod();
        break;
      case '-':
        v = v - this._prod();
        break;
    }
  }
  return v;
};

//a*b*...
scout.Calculator.prototype._prod = function() {
  var v = this._unary();
  while (this._next() === '*' || this._next() === '/') {
    switch (this._consumeNext()) { // NOSONAR
      case '*':
        v = v * this._unary();
        break;
      case '/':
        v = v / this._unary();
        break;
    }
  }
  return v;
};

//[+-]123, [+-](a)
scout.Calculator.prototype._unary = function() {
  var qualifier = 1;
  if (this._next() === '+') {
    this._consumeNext();
  } else if (this._next() === '-') {
    this._consumeNext();
    qualifier = -1;
  }
  var v;
  if ((v = this._group()) !== undefined) {
    return qualifier * v;
  }
  //must be num
  v = this._consumeNext();
  return qualifier * v;
};

//(a)
scout.Calculator.prototype._group = function() {
  if (this._next() === '(') {
    this._consumeNext();
    var v = this._expr();
    if (this._next() !== ')') {
      throw 'missing closing bracket';
    }
    this._consumeNext();
    return v;
  }
  return undefined;
};