JSON.Stringify() returns undefined instead of text

Question

I am making a form that downloads the data the user puts into it. So far the file downloads, but instead of the user's input it returns

[object Object]

I tried using JSON.Stringify(). But it is returning a file with "undefined" inside it. Even though the console.log() is giving me {username: "asdasd", password: "sdasdasd"}.

const handleSubmit = (e) => {
      e.preventDefault();
      console.log(formData);
      var formDataString = JSON.stringify(FormData);
      // ... submit to API or something
      download(formDataString, 'json.txt', 'text/plain');
    };
    const initialFormData = Object.freeze({
      username: "",
      password: "",
    });
    function download(formDataString, fileName, contentType) {
      var a = document.createElement("a");
      var file = new Blob([formDataString], {type: contentType});
      a.href = URL.createObjectURL(file);
      a.download = fileName;
      a.click();
  }

My full code is viewable here.

70ny · Accepted Answer · 2020-11-19 00:39:15Z

2

If you check lines 2 and 3 of snippet reported here, the answer is pretty simple: you're saying JSON.stringify(FormData) with capital F , while the console.log outputs formData with lower f

Variables are case-sensitive in JavaScript, so FormData is never defined (undefined), while formData is what you have correctly defined above, and console.log(formData) correctly outputs in the console the content of the variable.

answered Nov 19, 2020 at 0:39

70ny

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2 Comments

Dylan Bozarth Over a year ago

I can't believe it was right under my nose this whole time. Thank you. I'll accept this as the answer in 6 minutes

70ny Over a year ago

@imstupidpleasehelp can you imagine how many hours I wasted with similar errors? :) Don't worry, it's awlays like this: it's under our nose but we never see it! Personally, using IDEs such as WebStorm helped me a lot to avoid or identify mistakes like this.

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