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.

npm install evaluator.js

/**
 * 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;

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

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

• 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.

• 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.