{"id":514,"date":"2018-03-27T18:57:13","date_gmt":"2018-03-27T18:57:13","guid":{"rendered":"http:\/\/www.onux.com\/jspp\/blog\/?p=514"},"modified":"2018-03-27T19:11:19","modified_gmt":"2018-03-27T19:11:19","slug":"js-0-8-1-auto-catch-all-and-time","status":"publish","type":"post","link":"https:\/\/www.onux.com\/jspp\/blog\/js-0-8-1-auto-catch-all-and-time\/","title":{"rendered":"JS++ 0.8.1: auto, catch-all, and Time"},"content":{"rendered":"

JS++ 0.8.1 fixes two major bug fixes that appeared when we introduced generics (0.8.0) and introduces some very useful new features. If you come from a C++ background, you might appreciate some of the new syntax :-).<\/p>\n

‘auto’ Keyword<\/h3>\n

With the introduction of generic programming in 0.8.0, we need a more concise syntax to instantiate generic classes. The auto<\/code> keyword solves this problem.<\/p>\n

Now, instead of the following:<\/p>\n

\r\nVeryLongClassName<string> foo = new VeryLongClassName<string>();\r\n<\/pre>\n
You can instead instantiate classes using auto<\/code>:<\/p>\n
\r\nauto foo = new VeryLongClassName<string>();\r\n<\/pre>\n
auto<\/code> can be used for more than just generic classes though:<\/p>\n
\r\nclass Foo {}\r\n\r\nauto foo = new Foo();\r\n<\/pre>\n
The auto<\/code> keyword can only be used for variable declarations, and it reduces the redundancy of having to specify the type on the left-hand side only to repeat yourself on the right-hand side. This is known as local-variable type inference<\/strong> (to use the Java 10 terminology). For fans of C++, you may recognize this syntax.<\/p>\n
Catch-all Clauses<\/h3>\n
This is another syntax that comes from C++.<\/p>\n
Sometimes, you’ll want to catch an exception, but you don’t care to do anything with the exception object. In other cases, you may want to catch a specific type of exception but ignore all other exceptions. The “catch-all” clause can help you:<\/p>\n
\r\nimport System;\r\n\r\ntry {\r\n    throw new System.Exception();\r\n}\r\ncatch(System.Exception e) {\r\n    Console.log(e.getMessage());\r\n}\r\ncatch(...) {\r\n    Console.log(\"The catch-all clause provides no exception object but will catch all exceptions - whether the type of the exception is internal or external.\");\r\n}\r\n<\/pre>\n
\r\nimport Externals.JS;\r\n\r\ntry {\r\n    throw new ReferenceError();\r\n}\r\ncatch(...) {\r\n    Console.log(\"Do nothing\");\r\n}\r\n<\/pre>\n
System.Time.TimeUnits<\/h3>\n
JS++ has an emphasis on readability. Have you ever seen code that looks like this?<\/p>\n
\r\nsetInterval(function() { \/* ... *\/ }, 3600000);\r\n<\/pre>\n
The System.Time<\/a> module has been introduced for dealing with time. Specifically, we’ve introduced a TimeUnits<\/a> module to directly deal with the above case:<\/p>\n
\r\nimport System.Time;\r\nexternal setInterval;\r\n\r\nsetInterval(void() { \/* ... *\/ }, TimeUnits.hours(1));\r\n<\/pre>\n
Or, more succinctly:<\/p>\n
\r\nimport System.Time.TimeUnits;\r\nexternal setInterval;\r\n\r\nsetInterval(void() { \/* ... *\/ }, hours(1));\r\n<\/pre>\n
As always, we’ve had a focus on readable code. Here’s a preview of how well this composes:<\/p>\n
\r\nimport System;\r\nimport System.Time.TimeUnits;\r\n\r\nConsole.log(hours(1) + minutes(5));\r\n<\/pre>\n
Externals.Time<\/h3>\n
In JavaScript, functions such as setTimeout<\/code> and setInterval<\/code> are not part of the ECMAScript standard; they are provided by the host environment. Web browsers and Node.js ship with these functions, but it would not have been correct to add this to the Externals.JS<\/code> module. Therefore, we’ve introduced the Externals.Time<\/a> external module so you can more clearly work with timers.<\/p>\n
Bug Fixes<\/h3>\n