dd-formula-parser

Reserved Tokens

Operators

+, -, *, /

Parenthesis

(, )

Negative Sign

-

Functions

round, floor, ceil

Operands

Number Literals

Support decimal integer and float numbers, such as 18, 1.5

Variables

Besides reserved tokens and number literals, all the tokens are treated as variables, such as var1

A variable may be a reference to another formula. We supply api for resolving these references.

Api

parse(src, opt)

params

• src string of formula
• opt optional param
  • varValidator a function for validating variables, takes a single param of variable name. Returning boolean value false means the variable is invalid, and returning a string value to replace the variable name to what you returned.

return

This function return an nested array of objects representing each tokens in the formala.

Parentheses are represented with array.

Each operator is grouped with the operand after it unless the token after the operator is parenthesis.

Negative sign is grouped with the literal or variable it decorating unless it is followed by parenthesis. Negative sign decorating parenthesis is grouped with the operator before parenthesis or a "start" token.

Example

parse('-(var1 + 1) - -(-(var2 * 2) - 3) + -1.5 + -round(var3)', {
  varValidator: function (name) {
    if (name == 'var1') {
      return 'replaced';
    }
  }
});

{
  code: 0,
  data: [
    {type: 'start', negtive: true},
    [
      {type: 'var', name: 'replaced'},
      {type: 'const', name: 1, op: '+'}
    ],
    {type: 'op', name: '-', negtive: true},
    [
      {type: 'start', negtive: true},
      [
        {type: 'var', name: 'var2'},
        {type: 'const', name: 2, op: '*'}
      ],
      {type: 'const', name: 3, op: '-'}
    ],
    {type: 'const', name: -1.5, op: '+', negtive: true},
    {type: 'func', name: 'round', op: '+', negtive: true},
    [
      {type: 'var', 'name': 'var3'}
    ]
  ]
}

Description

• type type of token
  • start if a start of parenthesis contains negtive sign, we need this token to carry it.
  • op if an operator is followed by parenthesis, we need this token to carry it.
  • func functions
  • const number literals
  • var variables
• name representation of operators, functions, number literals and variables.
• op the operator grouped with the operand.
• negtive boolean value indicating whether the variables and expression grouped by parenthesis have a negtive sign.

stringify(items, opt)

This function is a negtive process of parse function. It takes an array param, and return an object with data property of formula string. It also accept the same optional param as parse.

return

{
  code: 0,
  data: 'var1 + 2'
}

If varValidator returned an Object type data, the return data of this function will be an array of string and objects as below.

{
  code: 0,
  arrayData: true,
  data: ['var1 + 2 + ', {var2: 1}, ' + 3']
}

genCalculator(src)

Generate calculator function for a formula string or the data returned by parse

return

{
  code: 0,
  data: [
    vars: ['var1', 'var2'],
    calculator: function (params) {...}
  ]
}

Description

• vars variable is in the formula
• calculator calculator function of the formula. The params must be supplied if the formula contains variables, it is a dictionary of variable name keys and the actual values of variables. This function returns a calculated number result.

resolveRefs(refMap, refName)

Recursively resolve the variables referring to other fomulas, replace them with the actual formula the are referring to.

params

• refMap a map of all the formulas, the key of the map is associated with the variable name.
• refName the key of the formula you want to resolve in the map.

return

{
  code: 0,
  data: '1 + 1'
}

Common Return Structure

All the functions return the same structure of data.

• code an integer for identifying the result. 0 zero means a success return, none zero means an error occurred.
• msg if code is none zero, this field indicates the reason.
• data the payload data

You can compare the code with error codes in PARSER_ERRS, STRINGIFIER_ERRS, REFS_RESOLVER_ERRS and CALCULATOR_GEN_ERRS exported to determin the error type.

Online Demo

https://codepen.io/webyom/pen/WKLedG