From ARROW function (es6) to ES5

Question

in my angularjs app I use esprima.js validation with gulp. And now, esprima throw me error for this two piece of js.

internal/streams/legacy.js:59
  throw er; // Unhandled stream error in pipe.
  ^

Error: Line 38843: Unexpected identifier

This is first piece

var filteredCampaignItems = campaignItems.filter((thing, index, self) => index === self.findIndex((t) => (
              t.expectedAdvertisementDisplayCount === thing.expectedAdvertisementDisplayCount && t.smartId === thing.smartId
            ))
          )

and second is filter for sum

app.filter('sumProduct', function() {
return function (input) {
var i = input instanceof Array ? input.length : 0;
var a = arguments.length;
if (i === 0)
  return i;
var total = 0;
for(var x of input){
  var duration = parseFloat(x.meta_duration);
  if(isNaN(duration)){
      throw 'filter sumProduct can count only numeric values';
  }
  total += duration;
}
return total;
}
});

Esprima version is "version": "4.0.0" and I found for instanbul dependecy that i need to get version "istanbul": "^1.0.0-alpha.2" , and i manually change to version 1.0.0-alpha.2 and call npm i esprima . I do this, but same error is throw.

Is there someone who know how to fix this?

Answer 1

I recommend to use BabelJS ( https://babeljs.io/ ).

Babel is a compiler that will convert every "new" features to "old" ES5 code (target-level is configurable, but I guess in most cases ES5 is fine)

They even have an online Tool to try it out live ( https://babeljs.io/repl/ )