Calculator

Calculator.js

/*
Problem Statement:
- Have the function Calculator(str) take the str parameter being passed and evaluate the mathematical expression within in. 
- For example, if str were "2+(3-1)*3" the output should be 8. 
- Another example: if str were "(2-0)(6/2)" the output should be 6. 
- There can be parenthesis within the string so you must evaluate it properly according to the rules of arithmetic. 
- The string will contain the operators: +, -, /, *, (, and ). 
- If you have a string like this: #/#*# or #+#(#)/#, then evaluate from left to right. So divide then multiply, and for the second one multiply, divide, then add. 
- The evaluations will be such that there will not be any decimal operations, so you do not need to account for rounding and whatnot.

Examples
Input: "6*(4/2)+3*1"
Output: 15
Input: "6/3-1"
Output: 1
*/

//Solves a mathematical expression with 2 operands and a operator
function operate(a, b, operator) {
    a = typeof a == 'string' ? parseInt(a) : a;
    b = typeof b == 'string' ? parseInt(b) : b;
    
    switch(operator){
		case "*": return a * b;
		case "/": return a / b;
		case "+": return a + b;
		case "-": return a - b;
    }
    return 0;
}
  
//Solves brackets and resolves mathematical expression inside it to a number. Uses breakString() method.
function removeBrackets(str) {
    while(str.includes('(')){
		var i = str.indexOf(')(')
		if(i != -1){
			str = str.substring(0,i+1) + '*' + str.substring(i+1,str.length);
		}
		var str2 = str.substring(str.indexOf("(") + 1, str.indexOf(")"));
		str = str.replace('('+str2+')', breakString(str2));  
    }
    return str;
}
  
//Solves a mathematical expression inside it to a number
function breakString(str) {
    var ops = ['-','+','*','/'];
    var result = 0;
  
    for(i=0; i<ops.length; i++) {
		if(str.includes(ops[i])){
			var a = str.substr(0,str.lastIndexOf(ops[i]));
			var b = str.substr(str.lastIndexOf(ops[i])+1,str.length-1);
			var op = ops[i];
	
			result = operate(
				isNaN(a) ? breakString(a): a,
				isNaN(b) ? breakString(b): b,
				op
			);
		}
    }
    return result;
}
  
function Calculator(str) { 
    var str2 = removeBrackets(str);
    return breakString(str2); 
}
     
console.log(Calculator("(4+5)/(1+2) + 2*(8-5)"));