I use Polymer 2.0 and my build setting is:
"builds": [
{
"name": "bundled",
"bundle": true,
"js": { "compile": true},
"css": { "minify": true },
"html": { "minify": true }
}]
I get "Can’t find variable: babelHelpers" error after build.
The Polymer CLI version that I use is 1.1.0.
EDIT: I was using polymer-cli locally. After installing latest polymer-cli globally, now I get “Constructor requires ‘new’ operator” on safari and “Failed to construct ‘HTMLElement’: Please use the ‘new’ operator, this DOM object constructor cannot be called as a function.” on chrome.
EDIT2: used webcomponents-loader.js instead of webcomponents-lite.js and my problem solved.