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I have include the blacklist option in my .babelrc file like

 blacklist: ["useStrict"]

and it's working fine.


You have few ways around this, bottom line setting modules to false either in .babelrc or your webpack since you use webpack


module : {
        loaders : [
                test: /\.js?/,
                include: APP_DIR,
                use: {
                    loader: 'babel-loader',
                    options: {
                        "presets": [
                            ['es2015', {modules: false}]
                exclude: /node_modules/

or .babelrc

    "presets": [
                "debug": true,
                "modules": false,
                "forceAllTransforms": true,
                "useBuiltIns": "usage"


Check out this package:

I was looking for a convenient way to get rid of the 'use strict' and it seems to be doing just that.


If you're seeing that error then most likely you've got somewhere in your codebase where you're declaring multiple properties on the same object. Disabling the alarm bell just fixes the symptom.

I've found this error to pop up if I declare duplicate properties in my JSX, e.g. when doing <MyComponent className="foo" onClick={onClick} className="foobar" /> or accidentally duplicating some other property.

Find and fix the actual error instead of just suppressing the error message. IE should tell you what line it's happening on and it shouldn't be too hard to look at what's there and figure out which component has the problem.

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