jquery calculate dynamic equation

Question

I need to perform calculation on dynamic string.

I will get an equation from db named rule through ajax. the rule may contain equation with operators like +,-,*,/,%.

how to perform this calculation?

  for (var i = 0; i < rules.length; i++) {
          var rule = rules[i].rule; // may contain $structurename1$*$structurename2$/$structurename3$ like this
          $('form :input[type="text"]').each(function(index,value){
              rule = rule.replace('$'+$(this).attr('structurename')+'$',$(this).val());
          });
  }

$('#result').val(rule);

Please provide us the code you've done yet so we can improve it all together. — pistou, Dec 02 '15 at 15:50
unsafe but `eval("(10+5)*2")`; That in itself is safe, but when you replace that with a user entered variable value, you are giving them access to run code via that eval. — Sterling Archer, Dec 02 '15 at 15:52
i have input string like this ** "70+30" ** and i just need the result should be "100" — karthikkumar subramaniam, Dec 02 '15 at 15:54
We have not asked you to describe your code, we have asked you to post it directly. — morganbaz, Dec 02 '15 at 15:55
http://stackoverflow.com/questions/6479236/calculate-string-value-in-javascript-not-using-eval# this post goes over a few options. — Sean Wessell, Dec 02 '15 at 16:01

score 1 · Answer 1 · edited May 23 '17 at 11:52

Calculate string value in javascript, not using eval

Using a combination of code from above link:

1. Strip anything in formula that thats not a number, parenthesis, OR operator.

2. evalulate formula as function

Modified to return NaN if the function errors due to invalid input. Which shouldn't happen due to the RegExp replacements in step 1.

function calc(fn) {
  var formula = fn.replace(/[^-()\d/*+.]/g, '');
  try {
    return new Function('return ' + formula)();
  } catch (err) {
    return NaN;
  }
}

DEMO: https://jsfiddle.net/tjywg716/

score -1 · Answer 2 · edited Dec 02 '15 at 16:54

-1

var str_expression=textbox1.text();
var result=eval(str_expression);
textbox2.text(result);

edited Dec 02 '15 at 16:54

Tomasz Jakub Rup

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answered Dec 02 '15 at 16:01

Gianluca Paris

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jquery calculate dynamic equation

2 Answers2