CODEWITHSUNDEEP
javascript
user2461391
user2461391

Reputation: 1433

Run inputted text as javascript in a javascript application?

My goal is to write a javascript application that will take text as an input and compile/run that text as code.

For example, say the JS application has a light that can turn red or green. The user inputted text could be lightRed(); to turn it red, and lightGreen(); to turn it green. I think the standard way to solve this kind of issue is to implement some kind of lexer/parser, like what Jison does.

However, I'm fairly new to JS programming and that seems like a daunting task - especially when I later plan to add more complex functionality to it like if/else statements. So I was wondering if it was possible to have the inputted text treated as javascript, essentially using the browser's ability to process javascript. So the javascript application will have a light, and it will have functions called lightRed() and lightGreen(). Text inputted to the javascript will be treated as javascript, so writing lightRed() as text will directly execute the lightRed() function in the application. Is this possible? Would this be more complicated than just using something like Jison? Thanks!

Upvotes: 0

Views: 131

Answers (2)

Joshua Dwire
Joshua Dwire

Reputation: 5443

The easiest way to compile the inputted JavaScript would be to use the eval function. This will evaluate and execute any code passed in as a string.

Example:

eval(document.getElementById('code').value)

JSFiddle

Be aware though that this does give the user the potential to execute any code that he wants without restriction, so think carefully before allowing this.

To help mitigate any security risk, you could execute the code in the global scope, as shown in this answer, preventing the code from accessing any of your local variables, and this would be just like if the user ran the code from their browser's developer console.

More Secure Example:

(function(){eval.apply(this,[document.getElementById('code').value])})()

More Secure JSFiddle

Upvotes: 6

asifrc
asifrc

Reputation: 5841

eval() will evaluate a string expression as JavaScript. Most people (including myself) will warn you about security holes; but if you think about it, the user could open up the javascript console and type and run all the same code.. So go for it :)

Upvotes: 1

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