mathjs/src/expression/transform/utils/compileInlineExpression.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif

'use strict'
function factory (type, config, load, typed) {
  /**
   * Compile an inline expression like "x > 0"
   * @param {Node} expression
   * @param {Object} math
   * @param {Object} scope
   * @return {function} Returns a function with one argument which fills in the
   *                    undefined variable (like "x") and evaluates the expression
   */
  return function compileInlineExpression (expression, math, scope) {
    // find an undefined symbol
    const symbol = expression.filter(function (node) {
      return type.isSymbolNode(node) &&
          !(node.name in math) &&
          !(node.name in scope)
    })[0]

    if (!symbol) {
      throw new Error('No undefined variable found in inline expression "' + expression + '"')
    }

    // create a test function for this equation
    const name = symbol.name // variable name
    const subScope = Object.create(scope)
    const eq = expression.compile()
    return function inlineExpression (x) {
      subScope[name] = x
      return eq.eval(subScope)
    }
  }
}

exports.factory = factory