readAsBinaryString メソッドは、 指定された Blob ないし File オブジェクトを読み込むために使用します。 読込処理が終了すると readyState は DONE に変わり、loadend イベントが生じます。それと同時に result プロパティには生のバイナリデータを文字列で解釈したものが格納されます。
現在このメソッドは2012年7月12日付の W3C 草案に従って廃止されています。
構文
instanceOfFileReader.readAsBinaryString(blob);
パラメータ
例
var canvas = document.createElement('canvas');
var height = 200;
var width = 200;
canvas.width = width;
canvas.height = height;
var ctx = canvas.getContext('2d');
ctx.strokeStyle = '#090';
ctx.beginPath();
ctx.arc(width/2, height/2, width/2 - width/10, 0, Math.PI*2);
ctx.stroke();
canvas.toBlob(function (blob) {
var reader = new FileReader();
reader.onloadend = function () {
console.log(reader.result);
}
reader.readAsBinaryString(blob);
});
仕様
| Specification | Status | Comment |
|---|---|---|
| File API The definition of 'FileReader' in that specification. |
Working Draft | Initial definition |
ブラウザ実装状況
| Feature | Firefox (Gecko) | Chrome | Edge | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|---|
| Basic support | 3.6 (1.9.2)[1] | 7 | (Yes) | 10 | 12.02[2] | 6.0 |
| Support in Web Workers | 46 (46) | (Yes) | (Yes) | No support | (Yes) | No support |
error property uses DOMException, not DOMError |
58 (58) | (Yes) | (Yes) | No support | (Yes) | No support |
| Feature | Firefox Mobile (Gecko) | Android | Edge | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | 32 | 3 | (Yes) | 10 | 11.5 | 6.1 |
| Support in Web Workers | 46.0 (46) | (Yes) | (Yes) | No support | (Yes) | No support |
error property uses DOMException, not DOMError |
58.0 (58) | ? | (Yes) | No support | (Yes) | No support |
[1] Prior to Gecko 2.0 beta 7 (Firefox 4.0 beta 7), all Blob parameters below were File parameters; this has since been updated to match the specification correctly. Prior to Gecko 13.0 (Firefox 13.0 / Thunderbird 13.0 / SeaMonkey 2.10) the FileReader.error property returned a FileError object. This interface has been removed and FileReader.error is now returning the DOMError object as defined in the latest FileAPI draft.
[2] Opera has partial support in 11.1.