error

Author: wang-jun-coder

Error:Debugger/Error/index.js

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+
+//************ javascript 错误 ***************
+// `<EvalError>` eval 执行  出错, 该错误类型已经不再在ES5中出现了，只是为了保证与以前代码兼容，才继续保留
+// eval('xxx'); //ReferenceError: xxx is not defined
+
+// `<SyntaxError>` js 语法错误
+// const i-1;      // SyntaxError: Missing initializer in const declaration
+
+// `<RangeError>` 数组越界错误
+// const array = new Array(-1); // RangeError: Invalid array length
+
+// `<ReferenceError>` 引用错误
+// const a = b;    // ReferenceError: b is not defined
+
+// `<TypeError>` 对象类型错误
+// const c = (null).c; // TypeError: Cannot read property 'c' of null
+
+// `<URIError>` url 错误
+// decodeURI('%');  // URIError: URI malformed
+
+
+//****************** 操作系统错误 **************************
+// 由底层操作系触发的系统错误，例如试图打开不存在的文件
+// const fs = require('fs');
+// fs.openSync('x.js'); // Error: ENOENT: no such file or directory, open 'x.js'
+
+// 权限不足
+// const os = require('os');
+// os.setPriority(-1); //SystemError [ERR_SYSTEM_ERROR]: A system error occurred: uv_os_setpriority returned EACCES (permission denied)
+
+// 端口占用
+// const http = require('http');
+// http.createServer().listen(3000);
+// http.createServer().listen(3000);   // Error: listen EADDRINUSE: address already in use :::3000
+
+
+// ******************* 用户自定义错误 ****************
+// throw new Error('CustomError'); // Error: CustomError
+
+
+// ******************* 断言错误 ****************
+// const assert = require('assert');
+// assert.strictEqual(1, 2, 'assert error');   // AssertionError [ERR_ASSERTION]: assert error
+
+
+
+
+// 错误捕获
+
+// error first
+// const fs = require('fs');
+// fs.readFile('xxx.js', (err, data) => {
+//     if (err) {
+//         console.log(err);   // { [Error: ENOENT: no such file or directory, open 'xxx.js'] errno: -2, code: 'ENOENT', syscall: 'open', path: 'xxx.js' }
+//         return;
+//     }
+//     console.log(data);
+// });
+
+// try catch
+// try {
+//     a ++;
+// } catch (e) {
+//     console.log(e); //ReferenceError: a is not defined
+// }
+
+// // EventEmitter on error
+// const EventEmitter = require('events');
+//
+// const emitter = new EventEmitter();
+// emitter.on("error", error => {
+//     console.log(error); // Error: Some Error
+// });
+// emitter.emit("error", new Error('Some Error'));
+
+// // uncaughtException, 非常规手段
+// process.on("uncaughtException", (error) => {
+//     console.log(error)  // ReferenceError: i is not defined
+// });
+// i++;
+
+// promise unhandledRejection(未监听 uncaughtException时有效)
+// process.on("unhandledRejection", (reason, p) => {
+//    console.log(`${reason} ${p}`);   // unhandledRejection [object Promise]
+// });
+// Promise.reject('unhandledRejection');
+
+
+// 异步导致堆栈丢失
+const throwError = () => {
+    throw new Error();
+};
+
+const doSth = () => {
+    setImmediate(() => throwError());
+};
+
+const main = () => {
+    doSth();
+};
+
+main();
+/**
+ throw new Error();
+ ^
+
+ Error
+ at throwError (/Users/wangjun/Desktop/practice/opensource/node-every-day/Error:Debugger/Error/index.js:91:11)
+ at Immediate.setImmediate (/Users/wangjun/Desktop/practice/opensource/node-every-day/Error:Debugger/Error/index.js:95:24)
+ at runCallback (timers.js:705:18)
+ at tryOnImmediate (timers.js:676:5)
+ at processImmediate (timers.js:658:5)
+ * */
+

Error:Debugger/error.md

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+# Error
+
+### 错误分类
+
+标准 JavaScript 错误
+
+```js
+//************ javascript 错误 ***************
+// `<EvalError>` eval 执行  出错, 该错误类型已经不再在ES5中出现了，只是为了保证与以前代码兼容，才继续保留
+eval('xxx'); //ReferenceError: xxx is not defined
+
+// `<SyntaxError>` js 语法错误
+const i-1;      // SyntaxError: Missing initializer in const declaration
+
+// `<RangeError>` 数组越界错误
+const array = new Array(-1); // RangeError: Invalid array length
+
+// `<ReferenceError>` 引用错误
+const a = b;    // ReferenceError: b is not defined
+
+// `<TypeError>` 对象类型错误
+const c = (null).c; // TypeError: Cannot read property 'c' of null
+
+// `<URIError>` url 错误
+decodeURI('%');  // URIError: URI malformed
+```
+
+系统错误	
+
+```js
+//****************** 操作系统错误 **************************
+// 由底层操作系触发的系统错误，例如试图打开不存在的文件
+const fs = require('fs');
+fs.openSync('x.js'); // Error: ENOENT: no such file or directory, open 'x.js'
+
+// 权限不足
+const os = require('os');
+os.setPriority(-1); //SystemError [ERR_SYSTEM_ERROR]: A system error occurred: uv_os_setpriority returned EACCES (permission denied)
+
+// 端口占用
+const http = require('http');
+http.createServer().listen(3000);
+http.createServer().listen(3000);   // Error: listen EADDRINUSE: address already in use :::3000
+```
+
+用户自定义错误	
+
+```js
+// ******************* 用户自定义错误 ****************
+throw new Error('CustomError'); // Error: CustomError
+```
+
+断言错误	
+
+```js
+// ******************* 断言错误 ****************
+const assert = require('assert');
+assert.strictEqual(1, 2, 'assert error');   // AssertionError [ERR_ASSERTION]: assert error
+```
+
+
+### 错误捕获
+
+error first（约定，非强制）
+
+```js
+const fs = require('fs');
+fs.readFile('xxx.js', (err, data) => {
+    if (err) {
+        console.log(err);   // { [Error: ENOENT: no such file or directory, open 'xxx.js'] errno: -2, code: 'ENOENT', syscall: 'open', path: 'xxx.js' }
+        return;
+    }
+    console.log(data);
+});
+```
+
+try catch
+
+```js
+try {
+    a ++;
+} catch (e) {
+    console.log(e); //ReferenceError: a is not defined
+}
+```
+
+EventEmitter on error
+
+```js
+const EventEmitter = require('events');
+
+const emitter = new EventEmitter();
+emitter.on("error", error => {
+    console.log(error); // Error: Some Error
+});
+emitter.emit("error", new Error('Some Error'));
+```
+
+uncaughtException(非常规手段，需正确使用)
+
+```js
+// uncaughtException, 非常规手段
+process.on("uncaughtException", (error) => {
+    console.log(error)  // ReferenceError: i is not defined
+});
+i++;
+```
+
+unhandledRejection(promise 未 catch，且未监听 uncaughtException)
+
+```js
+process.on("unhandledRejection", (reason, p) => {
+   console.log(`${reason} ${p}`);   // unhandledRejection [object Promise]
+});
+Promise.reject('unhandledRejection');
+```
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