CODEWITHSUNDEEP
javascriptrhino
J. Douglas
J. Douglas

Reputation: 67

Is there a way to have optional parameters in a javascript function when calling the script from Rhino?

I have written a javascript project which makes extensive use of default parameters, for example:

function hello(x = true){
    ...
}

Now I want to call my code from the command line. I have tried using Rhino, Nashorn and Node but they all throw errors when encountering default parameters. In Rhino the error is:

js: "resource.js", line 6: missing ) after formal parameters
js: function hello(x = true){
js: ..................^
js: "resource.js", line 1: Compilation produced 1 syntax errors.

Is there some way I can call my project from the command line without having to rewrite all my code to get rid of default arguments?

Thanks

EDIT: after updating node.js to version 8 from version 4, this works. I will use node.js but I still don't know if this is possible on rhino.

Upvotes: 2

Views: 3396

Answers (1)

aveuiller
aveuiller

Reputation: 1551

You always have a way to copy the behavior of default arguments but it won't as readable as with a newer version of javascript.

The straightforward way of doing it if you only have one argument would be an undefined check inside your function, i.e.: 

js> function hello(x){
  >   if (x === undefined) x = 5;
  >   return x;
  > }
js> hello()
5
js> hello(42)
42

On the other hand, if your function contains more arguments I would recommend you to use an object as input and then check for an undefined value, as above:

js> function hello(args){                              
  >   if (args.x === undefined) args.x = 5;     
  >   return args.x + "-" + args.y;
  > }
js> hello({y: 12})   
5-12
js> hello({x: 1, y: 42})
1-42

Upvotes: 1

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