ChaiJS
check-error

Error comparison and information related utility for node and the browser.

## What is Check-Error? Check-Error is a module which you can use to retrieve an Error's information such as its `message` or `constructor` name and also to check whether two Errors are compatible based on their messages, constructors or even instances. ## Installation ### Node.js `check-error` is available on [npm](http://npmjs.org). To install it, type: $ npm install check-error ### Browsers You can also use it within the browser; install via npm and use the `check-error.js` file found within the download. For example: ```html ``` ## Usage The primary export of `check-error` is an object which has the following methods: * `compatibleInstance(err, errorLike)` - Checks if an error is compatible with another `errorLike` object. If `errorLike` is an error instance we do a strict comparison, otherwise we return `false` by default, because instances of objects can only be compatible if they're both error instances. * `compatibleConstructor(err, errorLike)` - Checks if an error's constructor is compatible with another `errorLike` object. If `err` has the same constructor as `errorLike` or if `err` is an instance of `errorLike`. * `compatibleMessage(err, errMatcher)` - Checks if an error message is compatible with an `errMatcher` RegExp or String (we check if the message contains the String). * `getConstructorName(errorLike)` - Retrieves the name of a constructor, an error's constructor or `errorLike` itself if it's not an error instance or constructor. * `getMessage(err)` - Retrieves the message of an error or `err` itself if it's a String. If `err` or `err.message` is undefined we return an empty String. ```js var checkError = require('check-error'); ``` #### .compatibleInstance(err, errorLike) ```js var checkError = require('check-error'); var funcThatThrows = function() { throw new TypeError('I am a TypeError') }; var caughtErr; try { funcThatThrows(); } catch(e) { caughtErr = e; } var sameInstance = caughtErr; checkError.compatibleInstance(caughtErr, sameInstance); // true checkError.compatibleInstance(caughtErr, new TypeError('Another error')); // false ``` #### .compatibleConstructor(err, errorLike) ```js var checkError = require('check-error'); var funcThatThrows = function() { throw new TypeError('I am a TypeError') }; var caughtErr; try { funcThatThrows(); } catch(e) { caughtErr = e; } checkError.compatibleConstructor(caughtErr, Error); // true checkError.compatibleConstructor(caughtErr, TypeError); // true checkError.compatibleConstructor(caughtErr, RangeError); // false ``` #### .compatibleMessage(err, errMatcher) ```js var checkError = require('check-error'); var funcThatThrows = function() { throw new TypeError('I am a TypeError') }; var caughtErr; try { funcThatThrows(); } catch(e) { caughtErr = e; } var sameInstance = caughtErr; checkError.compatibleMessage(caughtErr, /TypeError$/); // true checkError.compatibleMessage(caughtErr, 'I am a'); // true checkError.compatibleMessage(caughtErr, /unicorn/); // false checkError.compatibleMessage(caughtErr, 'I do not exist'); // false ``` #### .getConstructorName(errorLike) ```js var checkError = require('check-error'); var funcThatThrows = function() { throw new TypeError('I am a TypeError') }; var caughtErr; try { funcThatThrows(); } catch(e) { caughtErr = e; } var sameInstance = caughtErr; checkError.getConstructorName(caughtErr) // 'TypeError' ``` #### .getMessage(err) ```js var checkError = require('check-error'); var funcThatThrows = function() { throw new TypeError('I am a TypeError') }; var caughtErr; try { funcThatThrows(); } catch(e) { caughtErr = e; } var sameInstance = caughtErr; checkError.getMessage(caughtErr) // 'I am a TypeError' ```