How do you write an arithmetic expression parser in JavaScript, without using eval or a constructor function?

Question

Given a string:

 var str1 = \"25*5+5*7\";

Without using eval or the constructor function in JavaScript, how would I be able to

Answer 1

You can use the expression parser of math.js:

var str1= "25*5+5*7"
document.write(str1 + ' = ' + math.eval(str1)); 
// output: "25*5+5*7 = 160"