JavaScript readAsBinaryString Function on E11

Question

In this page http://www.html5rocks.com/en/tutorials/file/dndfiles/ if you scroll down to example \"Example: Slicing a file. Try it!\" you will see uses of readAsBin

Answer 1

I had some problems with the answers here and ended up making a few slight changes.

Instead of assigning to pt.content, my solution is to send a custom object to the prototype's onload, that receiver can specifically look for, I named this property msieContent so it will be very specific.

Also I used other accepted answer for converting Uint8Array to string in more robust way, you can see full details of it here: https://stackoverflow.com/a/12713326/213050

Polyfill

if (FileReader.prototype.readAsBinaryString === undefined) {
    // https://stackoverflow.com/a/12713326/213050
    function Uint8ToString(u8a: Uint8Array) {
        const CHUNK_SZ = 0x8000;
        let c = [];
        for (let i = 0; i < u8a.length; i += CHUNK_SZ) {
            c.push(String.fromCharCode.apply(null, u8a.subarray(i, i + CHUNK_SZ)));
        }
        return c.join('');
    }
    FileReader.prototype.readAsBinaryString = function (fileData) {
        const reader = new FileReader();
        reader.onload = () => this.onload({
            msieContent: Uint8ToString(new Uint8Array(reader.result))
        });
        reader.readAsArrayBuffer(fileData);
    }
}

Usage

private _handleTextFile(file: File) {
    const reader = new FileReader();

    reader.onload = (e) => {
        // support for msie, see polyfills.ts
        const readResult: string = (e).msieContent || e.target.result;

    };

    reader.readAsBinaryString(file);
}