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Evaluator.js

Evaluator.js is a small, zero-dependency module for evaluating mathematical expressions.

All major operations, constants, and methods are supported. Additionally, Evaluator.js intelligently reports invalid syntax, such as a misused operator, missing operand, or mismatched parentheses.

Evaluator.js is used by a desktop calculator application of the same name. See a live demo on the website.

Installation

npm install evaluator.js

API

/**
 * Takes a string and evaluates the result.
 *
 * @param {string} expression The string.
 *
 * @throws {Error} No input.
 * @throws {Error} No valid tokens.
 * @throws {Error} Misused operator: <token>.
 * @throws {Error} Mismatched parentheses.
 * @throws {Error} Invalid token: <token>.
 * @throws {Error} No operations.
 * @throws {Error} Insufficient arguments for method: <token>.
 * @throws {Error} Insufficient operands for operator: <token>.
 * @throws {Error} Division by zero.
 * @throws {Error} Insufficient operators.
 *
 * @returns {number} The result.
 */
export default function (expression: string): number;

Examples

import evaluate from 'evaluator.js';

evaluate('8 / (2 + 2.75)');    // 1.68421053
evaluate('pi / 1.3');          // 2.41660973
evaluate('sum(5, 10, 50, -5)') // 60
evaluate('194 % 5');           // 4
evaluate('mean(12, 25, 1, 7)') // 11.25
evaluate('-8 - -3');           // -5
evaluate('acos(0)');           // 1.57079633
evaluate('((6 - 9) / 5) * 9'); // -5.4
evaluate('-e ^ -2');           // -0.13533528

Reference

Operators

  • + - Add / Unary Plus
  • - - Subtract / Unary Minus
  • * - Multiply
  • / - Divide
  • ^ - Power
  • % - Modulo
  • ( - Begin Group
  • ) - End Group
  • , - Separate Argument

Constants

  • E - Euler's constant and the base of natural logarithms.
  • LN2 - Natural logarithm of 2.
  • LN10 - Natural logarithm of 10.
  • LOG2E - Base 2 logarithm of E.
  • LOG10E - Base 10 logarithm of E.
  • PHI - Golden ratio.
  • PI - Ratio of the circumference of a circle to its diameter.
  • SQRT1_2 - Square root of 1/2.
  • SQRT2 - Square root of 2.
  • TAU - Ratio of the circumference of a circle to its radius.

Methods

  • ABS(x) - Returns the absolute value of a number.
  • ACOS(x) - Returns the arccosine of a number.
  • ACOSH(x) - Returns the hyperbolic arccosine of a number.
  • ADD(x, y) - Returns the total of two numbers.
  • ASIN(x) - Returns the arcsine of a number.
  • ASINH(x) - Returns the hyperbolic arcsine of a number.
  • ATAN(x) - Returns the arctangent of a number.
  • ATANH(x) - Returns the hyperbolic arctangent of a number.
  • ATAN2(y, x) - Returns the arctangent of the quotient of the arguments.
  • CBRT(x) - Returns the cube root of a number.
  • CEIL(x) - Returns the smallest integer greater than or equal to a number.
  • COS(x) - Returns the cosine of a number.
  • COSH(x) - Returns the hyperbolic cosine of a number.
  • DIVIDE(x, y) - Returns the quotient of two numbers.
  • EXP(x) - Returns E to the power of x.
  • EXPM1(x) - Returns subtracting 1 from EXP(x).
  • FACTORIAL(x) - Returns the factorial of x.
  • FLOOR(x) - Returns the largest integer less than or equal to a number.
  • HYPOT(x[, y[, ...]]) - Returns the square root of the sum of squares of the arguments.
  • LOG(x) - Returns the natural logarithm of a number.
  • LOG1P(x) - Returns the natural logarithm of 1 + x.
  • LOG10(x) - Returns the base 10 logarithm of a number.
  • LOG2(x) - Returns the base 2 logarithm of a number.
  • MAX(x[, y[, ...]]) - Returns the largest of one or more numbers.
  • MEAN(x[, y[, ...]]) - Returns the mean of one or more numbers.
  • MIN(x[, y[, ...]]) - Returns the smallest of one or more numbers.
  • MOD(x, y) - Returns the modulus of two numbers.
  • MULTIPLY(x, y) - Returns the product of two numbers.
  • POW(x, y) - Returns base to the exponent power.
  • SIN(x) - Returns the sine of a number.
  • SINH(x) - Returns the hyperbolic sine of a number.
  • SQRT(x) - Returns the positive square root of a number.
  • SUBTRACT(x, y) - Returns the difference of two numbers.
  • SUM(x[, y[, ...]]) - Returns the sum of one or more numbers.
  • TAN(x) - Returns the tangent of a number.
  • TANH(x) - Returns the hyperbolic tangent of a number.