Code property in javascript functions

Question

function hello(){
 console.log('Goodbye');
}

is an object. Almost everything in js is object. We have name property on it and its hello, but what about code property? How can I access that? Also, do I have the code inside {} or the whole whats above?

• Ankit Agarwal: where is your name and code property?
• Learn on hard way: @AnkitAgarwal hello.name

Answer 1

The code of a function is not in a publicly accessible property. It's stored in an internal [[Code]] property, as specified in Creating Function Objects.

The toString() method of a function will return the entire function definition as a string.

• Learn on hard way: That is what I need. Thanks. Did not knew about [[Code]]. Not very occasional on the surface of the js code.

Answer 2

Also, do I have the code inside {} or the whole whats above?

For your method, use toString

hello.toString()

Demo

function hello(){
 console.log('Goodbye');
}
console.log(hello.toString());

And if you only want to access code between { and }, then (assuming it is not an arrow function)

var code = hello.toString();
code = code.substring( code.indexOf( "{" ) + 1 ); //remove code before first {
code = code.substring( 0, code.lastIndexOf( "}" ) - 1 ); //remove code from last }

If it is an arrow function, then

var hello = () => console.log('Goodbye');
var code = hello.toString();
code = code.substring( code.indexOf( "=>" ) + 2 ); //get the string after =>

• Learn on hard way: Is that the same thing as when I just do hello without () ?
• gurvinder372: @Learnonhardway Sorry I didn't get do hello without ().
• Barmar: @Learnonhardway console.log() calls toString() internally to get the string to display.
• Learn on hard way: @gurvinder372 Means, getting the code without invoking it.
• gurvinder372: @Learnonhardway you are not invoking the function, just getting its body by doing toString.