How Can You Safely Evaluate String Formulas in JavaScript Without Using Eval()?

Evaluating String Values in JavaScript without Eval

The eval() function in JavaScript poses security risks and can lead to code injection. To avoid these issues, it is recommended to explore alternative methods for evaluating formula strings.

One such alternative is the Function() constructor, which can evaluate a string of code and return the result. For example, consider the following string formula:

var apa = "12/5*9+9.4*2";

Instead of using eval(apa), you can use the Function() constructor to create a new function that represents the formula:

function evil(fn) {
  return new Function('return ' + fn)();
}

console.log(evil('12/5*9+9.4*2')); // => 40.4

The Function() constructor takes a string of code as an argument and returns a function object. The return statement within the string ensures that the result of the formula is returned. The console.log() function then displays the evaluated result.

Using the Function() constructor is a safer alternative to eval() as it does not execute arbitrary code from a string. It provides a more controlled and predictable way to evaluate string expressions in JavaScript.

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