npm install sheva

var parser = require("sheva")(); (function(){ var And = parser.And.bind(parser) var Or = parser.Or.bind(parser) var MoreThan = parser.MoreThan.bind(parser) var Optional = parser.Optional.bind(parser) var Is = parser.Is.bind(parser) var Digit = parser.Digit.bind(parser) var $ = parser.$.bind(parser) parser.token({ "LB" : Is("("), "RB" : Is(")"), "PLUS" : Is("+"), "MINUS" : Is("-"), "MUL" : Is("*"), "DIV" : Is("/"), "NUM" : (function () { var digits = MoreThan(0, Digit) var sign = Or(Is("-"), Is("+")) var dot = Is(".") return And(Optional(sign), digits, Optional(And(dot, digits))) })() }) parser.grammar({ "Expr" : And($("Term"), Optional(MoreThan(0, $("MoreExpr")))), "MoreExpr" : And($("TermOp"), $("Term")), "Term" : And($("Factor"), Optional(MoreThan(0, $("MoreTerm")))), "MoreTerm" : And($("FactorOp"), $("Factor")), "TermOp" : Or(Is("PLUS"), Is("MINUS")), "Factor" : Or($("P-Expr"), Is("NUM")), "P-Expr" : And(Is("LB"), $("Expr"), Is("RB")), "FactorOp" : Or(Is("MUL"), Is("DIV")) }) parser.action({ "NUM" : function (n) { n.extra = parseFloat(n.value) }, "Factor" : function (n) { n.extra = n.children[0].extra }, "MoreTerm" : function (n) { n.extra = n.children[1].extra }, "MoreExpr" : function (n) { n.extra = n.children[1].extra }, "P-Expr" : function (n) { n.extra = n.children[1].extra }, "Term" : function (n) { n.extra = n.children[0].extra var child = n.children[1] for (var i = 0; child && i < child.children.length; i+=2) { var FactorOp = child.children[i] var Factor = child.children[i+1] switch (FactorOp.value) { case "*": n.extra *= Factor.extra;break; case "/": n.extra /= Factor.extra;break; } } }, "Expr" : function (n) { n.extra = n.children[0].extra var child = n.children[1] for (var i = 0; child && i < child.children.length; i+=2) { var TermOp = child.children[i] var Term = child.children[i+1] switch (TermOp.value) { case "+": n.extra += Term.extra;break; case "-": n.extra -= Term.extra;break; } } }, }) console.log(parser.parse("Expr", "(1+2)*(3+4+5)")) })()