How to check if the number of open braces is equal to the number of close braces?

Question

How to check if the number of open braces is equal to the number of close braces using regular expressions?

Here is the code:

var expression1 = "count(machineId)+count(toolId)"; var expression2 = "count(machineId)+count(toolId))"; 

These are the 2 expressions, where in the expression1, the number of open brackets is equal to number of close brackets and in expression2, the number of open brackets is not equal to number of close brackets. I need a regular expression which counts the number of open brackets and close brackets and gives me the alert. I need to check for valid syntax too.

if(expression1.......){ // here goes the regular expression     alert("Matched"); } else{     alert("Not matched"); } 

Answer 1

var expression1 = "count(machineId)+count(toolId)"; var expression2 = "count(machineId)+count(toolId))";  if (matches(expression1)) {     alert("Matched"); // Triggered! } else {     alert("Not matched"); }  if (matches(expression2)) {     alert("Matched"); } else {     alert("Not matched"); // Triggered! }  function matches(str) {     try {         new Function(str);         return true;     }     catch (e) {         return !(e instanceof SyntaxError);     } } 

This works because new Function() will cause a syntax error if your code is wrong. Catching the error means you can handle it safely and do whatever you want. Another good thing is that it doesn't execute the code, it just parses it. Basically, you're leveraging your task to the browser's parser.

It doesn't use regex, but it does check if your code is valid. Thus, it tells you if the parentheses match.