Node.js Errors

The Node.js applications generally face four types of errors:

• Standard JavaScript errors i.e. <EvalError>, <SyntaxError>, <RangeError>, <ReferenceError>, <TypeError>, <URIError> etc.
• System errors
• User-specified errors
• Assertion errors

Node.js Errors Example 1

Let's take an example to deploy standard JavaScript error - ReferenceError.

File: error_example1.js

1. // Throws with a ReferenceError because b is undefined  
2. try {  
3.   const a = 1;  
4.   const c = a + b;  
5. } catch (err) {  
6.   console.log(err);  
7. }  

Open Node.js command prompt and run the following code:

1. node error_example1.js  

Node.js Errors Example 2

File: timer2.js

1. const fs = require('fs');  
2. function nodeStyleCallback(err, data) {  
3.  if (err) {  
4.    console.error('There was an error', err);  
5.    return;  
6.  }  
7.  console.log(data);  
8. }  
9. fs.readFile('/some/file/that/does-not-exist', nodeStyleCallback);  
10. fs.readFile('/some/file/that/does-exist', nodeStyleCallback);  

Open Node.js command prompt and run the following code:

1. node error_example2.js