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Javascript: check if an expression is evaluable or not?

I have a random expression that is given by users (for example: 2 + 3 * 5.21 * + (4) 7, * - 54 + 3). This expression can contain any number of operands or operators to form an expression. I need to evaluate this expression to get an answer. I tried to evaluate using the eval () function , but the problem is that the wrong expression passed to the eval () function , it throws an error and stops the program. I tried it with

if(eval(exp))
{    
    //Action Expression is evaluatable
}
else
{
    //expression is not Evaluatable
}

but didnt work and issued an error

"SyntaxError: unterminated regular expression literal."

Due to the variety in the nature of the expressions, it would be difficult for me to construct control statements before evaluating.
can you suggest how I can just check if the expression is passed to the eval () function correctly?

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2 answers


Catch the error:



try {
        eval(exp); 
    } catch (e) {
        if (e instanceof SyntaxError) {
            alert(e.message);
        }
    }
+4


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You can put the content of your script in a script tag on the fly and then check the return of the error function. Or define a variable at the end of your script and check if it exists after execution.



Or mayber you can find the answer here: fooobar.com/questions/121603 / ... !!

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