expression-eval.js

gistfile1.txt

var evalRPN = function(tokens) {
    var stack = [];
    while(tokens.length > 0){
      var c = tokens.shift();
      if(c == "+"){
        c = add(stack);
      }else if(c == "-"){
        c = sub(stack);
      }else if(c == "*"){
        c = mul(stack);
      }else if(c == "/"){
        c = div(stack);
      }
      stack.push(c);
      // console.log("tokens="+tokens);
      // console.log("stack="+stack);
    }
    return stack[0];
};
var add = function(arr) {
  var a2 = arr.pop();
  var a1 = arr.pop();
  return a2+a1;
}
var sub = function(arr) {
  var a2 = arr.pop();
  var a1 = arr.pop();
  return a1-a2;
}
var mul = function(arr) {
  var a2 = arr.pop();
  var a1 = arr.pop();
  return a2*a1;
}
var div = function(arr) {
  var a2 = arr.pop();
  var a1 = arr.pop();
  return a1/a2;
}
var prior = function(s){
  if(s == "+" || s == "-" ) return 0;
  if(s == "*" || s == "/" ) return 1;
  return -1;
}
var proc = function(expr,v){
  if(v.length>0){
    expr.push(parseInt(v));
  }
  return "";
}

var calculate = function(str) {
  var expr = [];
  var opr = [];
  var v = "";
  for(var i in str){
    var s=str[i];
    if(s != " ") {
      if(s == "("){
        opr.push(s);
        v=proc(expr,v);
      }else if(s == "+" || s == "-" || s == "*" || s == "/"){
      //   v=proc(expr,v);
      //   opr.push(s);
      // }else if(s == "+" || s == "-"){
        v=proc(expr,v);
        var p = opr[opr.length-1];
        while(prior(s)<=prior(p)){
          expr.push(opr.pop());
          p = opr[opr.length-1];
        }
        opr.push(s);
      }else if(s == ")"){
        v=proc(expr,v);
        var t = opr.pop();
        while (t!="(") {
          expr.push(t);
          t = opr.pop();
        }
      }else{
        v=v+s;
      }
    }
    // console.log("expr="+expr);
    // console.log("opr="+opr);
  }
  while (opr.length>0) {
    expr.push(opr.pop());
  }
  // console.log("str="+str);
  // console.log("expr="+expr);
  return evalRPN(expr);
};


var ex = "(110/2+(14+25*2+2)*3-103)+(16+80-7)";
console.log(ex+"="+calculate(ex));
ex = "( 130/5+(119/7- (15*3*4/5-5*3)+20*5)-3)+(62+108)";
console.log(ex+"="+calculate(ex));