What is the correct way to call a function from a string?

Question

Is it okay to do the following:

// Response from an API as a string, that contains a function to call.
const stringFunc = 'myFunc({"Status":200,"Message":"This is a message"})';

function myFunc(obj) {
  console.log(obj);
}

function callBack(stringFn) {
  return Function.prototype.call(stringFn);
}

callBack(stringFunc);

Console logs:

{"Status":200,"Message":"This is a message"}

It seems to work just fine, but wanted to know if this was the correct way to go about this at all? Are there any better methods or unforeseen implications?

Thanks

You can also call function by using eval : developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — kartik upadhyay
– kartik upadhyay, Commented Jan 12, 2017 at 13:20

Nitheesh · Accepted Answer · 2017-01-12 13:20:38Z

1

Use eval method.

<!DOCTYPE html>
<html>

<body>
    <script>
        const stringFunc = 'myFunc({"Status":200,"Message":"This is a message"})';

        function myFunc(obj) {
            console.log(obj);
        }

        function callBack(stringFn) {
            return Function.prototype.call(stringFn);
        }

        eval(stringFunc);
    </script>
</body>

</html>

answered Jan 12, 2017 at 13:20

Nitheesh

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3 Comments

Michael Giovanni Pumo Over a year ago

Why do you still have the callback() function though? Not needed if using eval(), right?

Nitheesh Over a year ago

No need of callBack if your intended to call myFunc only

NineBerry Over a year ago

Note that using eval() or using any other way to execute code from a string is a serious security issue. When the string comes from an untrusted source, an attacker can execute anything in the context of your web page. You should not do that.

hackerrdave · Accepted Answer · 2017-01-12 13:37:51Z

1

As an alternative to eval you can use the Function constructor:

const stringFunc = 'myFunc({"Status":200,"Message":"This is a message"})';

function myFunc(obj) {
  console.log(obj);
}

const payloadFunc = new Function(stringFunc);
payloadFunc() //logs the object

answered Jan 12, 2017 at 13:37

hackerrdave

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