To help you get started, we've collected the most common ways that math-expression-evaluator is being used within popular public projects.

MoOx / reduce-css-calc / index.js View on Github

var unit = units[0] || ""

    if (unit === "%") {
      // Convert percentages to numbers, to handle expressions like: 50% * 50% (will become: 25%):
      // console.log(expression)
      expression = expression.replace(/\b[0-9\.]+%/g, function(percent) {
        return parseFloat(percent.slice(0, -1)) * 0.01
      })
    }

    // Remove units in expression:
    var toEvaluate = expression.replace(new RegExp(unit, "gi"), "")
    var result

    try {
      result = mexp.eval(toEvaluate)
    }
    catch (e) {
      return functionIdentifier + "(" + expression + ")"
    }

    // Transform back to a percentage result:
    if (unit === "%") {
      result *= 100
    }

    // adjust rounding shit
    // (0.1 * 0.2 === 0.020000000000000004)
    if (functionIdentifier.length || unit === "%") {
      result = Math.round(result * decimalPrecision) / decimalPrecision
    }

View more ways to use math-expression-evaluator

math-expression-evaluator

An extremely efficient, flexible and amazing evaluator for Math expression in Javascript.

Use cases

Fiddle Yourself

Installation

Node JS

Using npm

npm install math-expression-evaluator

Browser

Using bower

bower install math-expression-evaluator

Usage

Using eval method of mexp object

const mexp = new Mexp() var value = mexp.eval(exp); // 2 + 2

Using constituents of eval methods of mexp object

1. Create mexp object

    const mexp = new Mexp
   

2. Parse an expression and then add additional detail to the tokens using

    var lexed = mexp.lex("expression");
   

   which returns an array of token which will be further processed by methods toPostfix and postfixEval

3. Now, that array is needed to be converted to postfix notation using

    var postfixed = mexp.toPostfix(lexed);  
   

   which converts the array to postfix notation and return new array

4. Now to get the value of expression use postfixEval

    var result = mexp.postfixEval(postfixed);  
   

   where result contains the result.

Extending tokens

1. Defining a token

   A token is defined similar way as 1.x version. You may refer to test file on examples on how to add tokens. Since this package is TS compatible, you will get autocomplete on mexp.addToken

2. Adding tokens using addToken method of mexp object

    const mexp = new Mexp()
    mexp.addToken([token1, token2]) // tokens once added will be preserved in later evaluations
   

3. Adding tokens using eval method of mexp object

    const mexp = new Mexp()
    mexp.eval("expression", [token1, token2]) // tokens once added will be preserved in later evaluations
   

4. Adding token using constituents of eval method of mexp object

    const mexp = new Mexp()
    const answer = mexp.postfixEval(mexp.toPostfix(mexp.lexed("expression", [token1, token2]))) // tokens once added will be preserved in later evaluations
    console.log(answer)
   

How to run test

npm test

Supported symbols

Features

Amazing support for Sigma and Pi

This is a fantastic feature of this calculator that it is capable of evaluating expressions containing Sigma and Pi. Passing Sigma(1,100,n) will evaluate to 5050 as n is summationed from 1 to 100. and Pi(1,15,n) will evaluate to 1307674368000 as n is multiplied from 1 to 15 which is equal to 15!

Parenthesis less expression

If a expression is readable by human then it is readable by this evaluator. There is no need to wrap every function inside parenthesis. For eg. sin90 will work totally fine instead of sin(90)

##Changelog

Removed lodash.indexof and used native Array.prototype.indexOf hence dropping suppports for IE8 and below.

This will reflect in next release named v1.2.16