— but they all do it differently. This makes generically identifying object and
class structures difficult, if not impossible. To make things worse — or
better, depending on who you ask — the language has a couple of powerful
holes programmers use to perform clever tricks that are otherwise difficult. One
example of this is wrapping major chunks of code in an
evalf(..) function, making it only valid at runtime. It's an issue
we're still struggling to model accurately in JSDT.
Without a language model, it's difficult or impossible to place code in context. Since many programming elements depend on the context of code, it's essential for tooling to establish context. IDEs that lack a model and code context also miss out on full type-resolution and validation, scope, visibility, or any of the other good validation essential for easy development.
Figure 1. JSDT language abstraction stack
The basic language model
Type and class inference
Exposing the model
Managing variable and member scope
Figure 2. JSDT library configuration
JSDT uses a library mechanism to manage common objects, variables, and types in a project. Libraries can be added to a project to provide object and variable sets specific to the users' target runtime environment. If two libraries exist that define conflicting members, the members are aggregated and noted in the user interface where relevant. This helps establish methods common across browsers or environments.
With the high-level design points out of the way, let's take a closer look at the features. A few of JSDT's less-visual — but essential — features include same-word highlighting, auto-closing of braces, parentheses, quotes, and auto-indention to name a few. It may suffice to say, "If a good IDE should have it, then JSDT supports it."
Figure 3. Content assistance
Error detection and correction
An IDE is most useful when it can actively determine code errors. The JSDT detects three major types of errors: grammar/language errors, types/fields/method visibility, and flow or logic errors. All error warning levels are individually configurable by way of the preference pages.
Figure 4. Unresolved method
JSDT attempts to resolve all fields and methods for an object. When a method can't be resolved, it's marked in error.
Figure 5. Syntax error
Syntax errors are also found and marked. Here, the
statement is missing a semicolon.
Figure 6. Flow analysis
Figure 6 demonstrates the flow analysis. Since any code after the
return statement is unreachable, it's marked in error.
Figure 7. Quick fix
Some errors have quick-fix options. In Figure 7, when the user clicked the error marker
next to the unresolved variable
formyValue, JSDT comes up with some options to correct the error.
Source gets messy at times. It's easy-to-read, well-structured, and well-formatted code. The problem is keeping code formatted while you develop and debug. JSDT supports many as-you-type formatting features, such as configurable auto-indent and character pair-matching. These are helpful for speed of development and readability.
Other JSDT features
The items above aren't the only features JSDT supports. Here's a full list of the self-explanatory (but must-have) JSDT features:
- Syntax highlighting
- Folding/line numbers
- Full outlining, showing classes, functions, and fields
- Highlight and check of matching brackets/parentheses
- Auto-complete of brackets, parentheses, and indentation
- Mark occurrence
- Comment toggle (line and block)
- Generate element JsDoc
- Surround with do, for, try/catch, while
- User-configurable completion templates
- Extract function/change function signature
- Indentation correction
- Open declaration
- Open-type hierarchy
- Open-call hierarchy
- Customizable code formating
- Full search
- Breakpoint support
- Defined browser libraries with JsDoc for Firefox, Internet Explorer, and ECMA-3
- Library image support
- Debugging support provided through the ATF Project
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