formik logo The purpose of this post is to show some things that some people might struggle with when starting working with . Formik If you do not yet know about Formik please refer to its or these posts: Github The Joy of forms with React and Formik Better React forms with Formik (written by me) Painless React Forms with Formik I’m gonna make these examples simple and understandable for demonstration purposes. I’m also going to leave out some features intentionally so I can throw some challenges at you in the end! Uploading one file 📎 I’m pretty sure all of us have tried file uploading in forms. In the Formik docs there are no indications or directions for file uploading but it as simple as handling a select box. react-select All you really need is an entry for the values of Formik (in this case called and setup the to use Formiks’ function. Remember we can easily access the uploaded file by using file) onChange setFieldValue event.currentTarget.files[0]! It’s easy as: and Formik holds the object for you. You can do whatever you want with it. Get the name, size and type? File So with all this data you can show the image in a little thumbnail below the input like so: thumbnail example Checkout the example below to see how you can easily accomplish this. For the thumbnail generation I went really simple. No need for fancy stuff for demonstration purposes. CodeSandbox.io one file upload with thumbnail example Uploading multiple files 📎 📎 📎 We’ve seen a single file upload but how about multiple files? And a dropzone? And thumbnails for those files? I’m gonna use the excellent lib to handle all those dropzone specifics. I’m also going to re-use the Thumbnail component from the previous example to keep things simple. react-dropzone This will be the end result 3 files uploaded Formik makes it easy to handle stuff like this. is all you need. Basically you can keep track of an array of files and do everything you need to. setFieldValue Feel free to play around with the CodeSandbox.io example below! Multiple file upload example reCaptcha Support 🔐 I wager almost everyone has interacted with some form of r in the past. Maybe even today you filled a form and ticked that box or played that little game to prove that you’re no bot. Point is, reCaptchas are pretty common when people want to prevent bots from spamming trash at them by continuously submitting their forms. Google eCaptcha Let me show you how you can handle a simple recaptcha on your form. For the example I’ll be using the package to get the api connection. react-recaptcha I’ve used a key that I only use for demonstration purposes. If for any reason it goes down by the time you’re reading this please feel free to input your own and try it out. Google reCaptcha v2 example What?! 😅 Were you expecting more work? Remember Formiks goal was to create a scalable, performant, form helper with a minimal API that does the really really annoying stuff, and leaves the rest up to you. Well we can simply control it ourselves with the function and handle it in values. Later you would submit it to the server and perform server side validation on the reCaptcha response given! setFieldValue All together! 💯 Great! You’ve come this far and now you want to know how you’ll apply this in a real scenario and submit the data to the server. Let me help! Let’s build a form for a user that has a and the form must be submitted by validating a reCaptcha. name, email, photo, some attachments In the end we’re gonna see how we should send things to the server in order for it to accept the files and the user model. the final form look As you can see in the below the form is only submitted when the recaptcha is verified and all our required fields are filled. Feel free to play around with it. CodeSandbox.io the full example Formik already handles and for free for us. So we just have got to plug the other fields in. It’s as simple as you think name email initial values, validation schema and submition code In order to get those files into the server you must submit them through . I went with the simple way because it works for demonstration purposes and I must keep it as simple and as clear for you. FormData I’m suggesting but you can use whatever you want! async/await const res = await fetch(“your post url”, { method: “POST”, body: formData }); And the rest is up to your server stack. NOTE: The piece of code below may have to differ depending on your backend stack. for (let i = 0; i <= values.attachments.length; i++) { formData.append(`attachments[${i}]`, values.attachments[i]); } Some challenges for you 🎲 At this point you might be wondering why I haven’t done some basic features like clearing the uploaded file, clearing individual uploaded files (from the multiple upload example) or maybe even clear and reset the reCaptcha. Well, that is challenge! 😏 😄 YOUR In order to brush up those skills free feel to fork up the CodeSandboxes and hack away! You can try Making a smarter Thumbnail component (react-dropzone actually gives us a preview blob so maybe use it? 😄) Removing a file from the single upload input Removing a(some) file(s) from the multiple upload input Reset the reCaptcha Simplify the FormData append code Make a real submission happen to some API Have fun coding away! 💻 🎲

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