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Download a File with Vue and Axios

You’re proud of how things are working out with your shiny new Vue SPA.  You’ve navigated your way over the authentication hurdle by implementing a token-based solution with Axios. Awesome!

You now realize how useful an Excel download of an existing browser-based report would be. Here comes the curve ball.  You have to download a file without using HTML links because we’re not using session IDs in cookies for authentication.

There are a few solutions to this. The path of least resistance is to use the authentication system you’ve already setup in your app.  That means using Axios to send a request using the pre-configured authentication header and then tell the browser to download the response.

You likely have something similar to this line of code somewhere in your front-end, sending the token authentication header.

this.axios.defaults.headers['Authorization'] = 
  'Bearer ' + this.store.state.accessToken;

With that in place, we’ll create a button in the component template to download the file.

<button @click="downloadExport">Excel Export</button>

Once that’s set, we’ll create a method in the component to send the request via Axios and tell the browser to download (not render) the response, the Excel file.

methods: {
    downloadExport() {
        this.axios.get('/v1/some-endpoint', {
            // If you forget this, your download will be corrupt.
            responseType: 'blob'
        }).then((response) => {
            // Let's create a link in the document that we'll
            // programmatically 'click'.
            const link = document.createElement('a');
    
            // Tell the browser to associate the response data to
            // the URL of the link we created above.
            link.href = window.URL.createObjectURL(
                new Blob([response.data])
            );
    
            // Tell the browser to download, not render, the file.
            link.setAttribute('download', 'report.xlsx');
    
            // Place the link in the DOM.
            document.body.appendChild(link);
    
            // Make the magic happen!
            link.click();
        }); // Please catch me!
    }
}

Now, of course, you should catch any rejections from the promise but you don’t need me for that.

I hope you found this helpful.   Have a suggestion to make this article better?  Let me know in a comment below.

Photo by Geetanjal Khanna on Unsplash

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