It does not use eval()
It uses regular expressions to parse [String] formulas "2+2" into [Number] formulas 2+2. Then it is performed as the common JavaScript arithmetic operation.

"2 + 2"  //4
"3*(5-2)"  //9
" 2.5  *   2.5  /   .1" //62.5
"3.5+5*(-4-(3/(3+1)-12*3-.2*22)-16/4*12-5/(2)+3.5+2.5*(1.5-2*7))-16" //-225.5
".25e+2*10" //250

Any bugs found? Give me to know on GitHub
If you need to perform arithmetic formulas with the floating point precision (avoid 0.30000000000000004 return values) or to perform arithmetic formulas with big numbers, check out exact-math package. It implements string-math features as the exactMath.formula method.

Installation

with NodeJS / bundlers

npm install string-math

var stringMath = require('string-math');

stringMath("--1") //1
stringMath("2/-2") //-1
stringMath("-5-5") //-10

with Browser

1. Add string-math.js to the HTML file.

<head>
  <script src="./string-math.js"></script>
</head>

Any other dependencies are needed.

2. Use `stringMath` global Function from `string-math.js`.

var result = stringMath("2+2");

Browser Support

Chrome	Firefox	IE	Safari	Opera
yes	yes	yes	yes	yes

Tests

> git clone https://github.com/devrafalko/string-math.git
> cd string-math
> npm install
> npm test
> npm test deep //displays error messages

Usage

`stringMath(expression[,callback])`

`expression` [String]

the arithmetical formula
it can contain:
- [0-9] digits
- 1.5, 0.5 or .5 decimal fractions
- -5, -.4, -5.55 negative values
- 2e-2, .25e+12, -3e-10 exponential notation values
- * multiplication sign
- / division sign
- + plus sign
- - subtraction sign
- ( and ) parentheses

`callback` [Function] (optional) (synchronous)

by default, if the callback argument is omitted and the expression is of incorrect type or is invalid, the Error object is thrown. If the callback is defined, the Error object is passed through the callback function, rather than being thrown.
if the [Function] callback argument is defined, it is called with the following arguments:
- [0] error
  It equals null, if the expression is of correct type and is valid math formula.
  Otherwise it equals Error object.
- [1] result
  It equals null if the expression is of incorrect type or if the math formula is invalid.
  Otherwise it equals [Number] result.

Return

If the math formula is of correct type and is valid, it returns the [Number] result. Otherwise it returns null.

Tips

the arithmetic order of operations is respected:
- parentheses first
- then division and multiplication (from left to right)
- then addition and subtraction (from left to right)
the multiplication sign can be omitted before parentheses; 4(2+1); equals to 4*(2+1)
the following signs combinations are allowed:
- 2 * -2; equals to 2 * (-2)
- 2 / -2; equals to 2 / (-2)
- +2 + 2; equals to 2 + 2
- 2 + +2; equals to 2 + 2
- -2 - -2 equals to -2 + 2
- -2 - +2 equals to -2 - 2
- -2 + -2 equals to -2 - 2
the (multi)spaces between values, signs and parentheses are allowed:
- 2 + 2
- 2 + ( -2 - -2)
- 2 + (+2 + +4 / -1)
- -.1 - -5
- 2 + 3e-5
- .25e+5 * -.25e-5
the spaces are not allowed between:
- negative sign and value: -2 - - 2
- period and digit in decimal fraction: 5 + . 3
- exponential notation formula: .2 e-5, 2e - 5, 3e +10

Keywords

FAQs

What is string-math?

Evaluates the result of the String arithmetical expression

Is string-math popular?

The npm package string-math receives a total of 3,071 weekly downloads. As such, string-math popularity was classified as popular.

Is string-math well maintained?

We found that string-math demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.

Package last updated on 18 Aug 2020

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Install

string-math

Description

Installation

with NodeJS / bundlers

with Browser

1. Add string-math.js to the HTML file.

2. Use stringMath global Function from string-math.js.

Browser Support

Tests

Usage

stringMath(expression[,callback])

expression [String]

callback [Function] (optional) (synchronous)