Next JS add data attributes to script tags

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When my Next JS app is compiled, it generates a list of script files to include like this.

<script src="/_next/static/chunks/main-1234.js" async=""></script>
<script src="/_next/static/chunks/webpack-1234.js" async=""></script>
<script src="/_next/static/chunks/framework.1234.js" async=""></script>
<script src="/_next/static/chunks/1234.5678.js" async=""></script>
<script src="/_next/static/chunks/commons.1234.js" async=""></script>
<script src="/_next/static/chunks/pages/_app-1234.js" async=""></script>
<script src="/_next/static/chunks/1234.5678.js" async=""></script>
<script src="/_next/static/chunks/pages/%5B%5B...path%5D%5D-1234.js" async=""></script>
<script src="/_next/static/1234/_buildManifest.js" async=""></script>
<script src="/_next/static/1234/_ssgManifest.js" async=""></script>

I want to add a custom data attribute to some of them like this.

<script data-cookieconsent="ignore" src="/_next/static/chunks/pages/%5B%5B...path%5D%5D-1234.js" async=""></script>

I've explored trying to do this in the next.config.js file as I know it's possible to make webpack overrides in there, but I'm not seeing a way to add data attributes to dynamically generated js files like this.

1 Answers

From Next.js 11

You'll need to extend and modify getScripts from the Head class in your _document.js file instead.

import Document, { Html, Head, Main, NextScript } from 'next/document'

class CustomHead extends Head {
    getScripts(files) {
        const originalScripts = super.getScripts(files);
        return originalScripts.map((script) => {
            return React.cloneElement(script, {
                'data-cookieconsent': this.props.cookieconsent
            });
        });
    }
}

class CustomDocument extends Document {
    render() {
        return (
            <Html>
                <CustomHead cookieconsent="ignore" />
                <body>
                    <Main />
                    <NextScript />
                </body>
            </Html>
        )
    }
}

export default CustomDocument

Before Next.js 11

An alternative solution is to extend the NextScript class in your _document.js file, as to include your custom data-* attribute in the scripts generated by Next.js.

import Document, { Html, Head, Main, NextScript } from 'next/document'

class CustomNextScript extends NextScript {
    getScripts(files) {
        const originalScripts = super.getScripts(files);
        return originalScripts.map((script) => {
            return React.cloneElement(script, {
                'data-cookieconsent': this.props.cookieconsent
            });
        });
    }
}

class CustomDocument extends Document {
    render() {
        return (
            <Html>
                <Head />
                <body>
                    <Main />
                    <CustomNextScript cookieconsent="ignore" />
                </body>
            </Html>
        )
    }
}

export default CustomDocument
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