Whilst doing some cleanup of some Aura Components for Summer 16, I was creating a JS function in my helper. I had wanted to add some default values to that function using the new ES6 Default Parameter Value Spec. Like so:
myFunction = function (param1 = "this", param2 = "that"){
...
}
Meaning that if I invoked this like
helper.myFunction();
> param1 = "this"
> param2 = "that"
helper.myFunction("what is");
> param1 = "what is"
> param2 = "that"
No luck. I get an error when I attempt to save the component on the server as such:
ERROR: 0Ad240000008RPA: org.auraframework.util.json.JsonStreamReader$JsonStreamParseException: Expected ‘,’ or ‘)’ [64, 30]: ‘=’
Answers:
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Method 1
I have just bumped in this issue and I would like to share my findings.
The following syntax is still not supported (you’ll get a JsonStreamParseException):
myFunction = function (param1 = "this", param2 = "that")
However, if you write it this way (without spaces around the equal signs), the default parameter values work fine:
myFunction = function (param1="this", param2="that")
I hope this will help someone.
Method 2
It turns out Lightning Components are using a version of closure compiler that is incompatible with this syntax currently. So as of Summer 16, certain syntax that is ES6 compliant will not work with Lightning Components.
I found this out through raising an issue with the aura open source framework repo in github.
Note: this is not an issue in Lightning Web Components
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