Evaluating a string as a mathematical expression in JavaScript

Question

How do I parse and evaluate a mathematical expression in a string (e.g. \'1+1\') without invoking eval(string) to yield its numerical value?

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Answer 1

I've recently done this in C# (no Eval() for us...) by evaluating the expression in Reverse Polish Notation (that's the easy bit). The hard part is actually parsing the string and turning it into Reverse Polish Notation. I used the Shunting Yard algorithm, as there's a great example on Wikipedia and pseudocode. I found it really simple to implement both and I'd recommend this if you haven't already found a solution or are looking for alternatives.