README

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.

Usage no npm install needed!