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Javascriptで巨大なテキストファイルを少しずつ読み込む ref: https://qiita.com/jiyu/items/3e29959758de497850b9
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| readBigTextForEachLine = (file, callback, chunk_size = 1024) => { | |
| let offset = 0; | |
| let text = ""; | |
| let slice = ""; | |
| let fr = new FileReader(); | |
| fr.onload = (event) => { | |
| if(typeof fr.result === "string") { | |
| callback(text + fr.result.replace(/\r/g, "\n")); | |
| return true; | |
| } | |
| let view = new Uint8Array(fr.result); | |
| for(let i=0, l=view.length; i<l; i++) { | |
| if(view[i] === 13) { // \n = 10 and \r = 13 | |
| if(view[i+1] === 10) { | |
| i++; | |
| } | |
| callback(text + "\n"); | |
| text = ""; | |
| continue; | |
| } | |
| text += String.fromCharCode(view[i]); | |
| } | |
| seek(); | |
| }; | |
| fr.onerror = () => { | |
| callback("Failed to read file."); | |
| }; | |
| let seek = () => { | |
| if (offset + chunk_size >= file.size) { | |
| slice = file.slice(offset); | |
| fr.readAsText(slice); | |
| } else { | |
| slice = file.slice(offset, offset + chunk_size); | |
| fr.readAsArrayBuffer(slice); | |
| } | |
| offset += chunk_size; | |
| } | |
| seek(); | |
| } |
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| <script> | |
| document.getElementById("upload").onchange = (e) => { | |
| let file = e.target.files[0]; | |
| readBigTextForEachLine(file, console.log); | |
| }; | |
| </script> | |
| <html><body> | |
| Upload Big File: <input type="file" id="upload"> | |
| </body></html> |
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