It sounds like your code is I/O bound. This means that multiprocessing isn’t going to help—if you spend 90% of your time reading from disk, having an extra 7 processes waiting on the next read isn’t going to help anything. And, while using a CSV reading module (whether the stdlib’s csv or something like NumPy … Read more
Those properties do not actually exist on the ArrayBuffer object. They are put there by the Dev Tools window for viewing the ArrayBuffer contents. You need to actually create the TypedArray of your choice through its constructor syntax new TypedArray(buffer [, byteOffset [, length]]); So in your case if you want Uint8Array you would need … Read more
This is prob not the best solution, BUT it worked for me. var reader = new FileReader(); reader.fileName = file.name // file came from a input file element. file = el.files[0]; reader.onload = function(readerEvt) { console.log(readerEvt.target.fileName); }; Not the best answer, but a working one.
FileReader API is asynchronous so you should handle it with block calls. A for loop wouldn’t do the trick since it wouldn’t wait for each read to complete before reading the next chunk. Here’s a working approach. function parseFile(file, callback) { var fileSize = file.size; var chunkSize = 64 * 1024; // bytes var offset … Read more
Hook version: const [image, setImage] = useState(null) const onImageChange = (event) => { if (event.target.files && event.target.files[0]) { setImage(URL.createObjectURL(event.target.files[0])); } } return ( <div> <input type=”file” onChange={onImageChange} className=”filetype” /> <img alt=”preview image” src={image}/> </div> ) Class version render() { return ( <div> <input type=”file” onChange={onImageChange} className=”filetype” /> <img alt=”preview image” src={this.state.image}/> <div/> ) } onImageChange … Read more
The problem is you’re running the loop now but the callbacks you are setting are getting run later (when the events fire). By the time they run, the loop is over and remains at whatever the last value was. So it will always show “file2” in your case for the name. The solution is to … Read more
Your application is failing for big files because you’re reading the full file into memory before processing it. This inefficiency can be solved by streaming the file (reading chunks of a small size), so you only need to hold a part of the file in memory. A File objects is also an instance of a … Read more
We modified midos answer to get it to work the following: function readFile(file){ return new Promise((resolve, reject) => { var fr = new FileReader(); fr.onload = () => { resolve(fr.result ) }; fr.onerror = reject; fr.readAsText(file.blob); }); }
You have to wait for the image to load. Try handling the element inside .onload. I’ve also simplified the process of setting the source of the two elements to how you should be doing it (with jQuery). reader.onload = (function(theFile) { var image = new Image(); image.src = theFile.target.result; image.onload = function() { // access … Read more