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| const fs = require("fs") | |
| const path = require("path") | |
| function example(message, callback) { | |
| const filePath = path.join(process.cwd(), "callback-file-test") | |
| const data = Buffer.from(message) | |
| fs.access(filePath, fs.constants.F_OK, (err) => { | |
| if (!err) { | |
| return callback(new Error("can't proceed, the file exists")) | |
| } | |
| fs.writeFile(filePath, data, (err) => { | |
| if (err) { | |
| return callback(new Error(`failed to write to the file: ${err.message}`)) | |
| } | |
| callback(null, filePath) | |
| }) | |
| }) | |
| } | |
| const message = `Walking the edges of reality, is it just me?` | |
| example(message, (err, filePath) => { | |
| if (err) { | |
| console.error(new Error(`something unexpected happened: ${err.message}`)) | |
| return | |
| } | |
| console.log("Successfully wrote to the file at", filePath) | |
| }) | |
| // $ node callback.js | |
| // Successfully wrote to the file at /home/zignd/code/error-handling-nodejs/callback-file-test | |
| // $ node callback.js | |
| // Error: something unexpected happened: can't proceed, the file exists | |
| // at /home/zignd/code/error-handling-nodejs/callback.js:26:23 | |
| // at /home/zignd/code/error-handling-nodejs/callback.js:10:20 | |
| // at FSReqCallback.oncomplete (fs.js:155:23) |
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