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typescript-plus

TypeScript is a language for application-scale JavaScript, For more information, please visit : TypeScript.

The typescript-plus compiler provides extra features to the original typescript compiler, such as accessors optimization, class reflection, conditional compilation and the most useful one: automatically reordering the source files by analyzing their dependencies in code. This compiler is integrated into the Egret Engine and has been heavily used by it.

This project will try to stay up to date with the new release of the original TypeScript project.

Current TypeScript Version: 3.1.3

Installing

First, make sure you have installed the latest version of node.js (You may need to restart your computer after this step).

For use as a command line app:

npm install -g typescript-plus

For programmatic use:

npm install typescript-plus

Usage

tsc-plus [input files] [options]

To learn how to use the original typescript compiler, please visit the following links:

• Quick tutorial
• Programming handbook
• Language specification
• Homepage

Extra Options

Option	Type	Default	Description
accessorOptimization	boolean	false	If an accessor contains only one call to another method, use that method to define the accessor directly.
emitReflection	boolean	false	Emit the reflection data of the class.
reorderFiles	boolean	false	Automatically reordering the source files by dependencies.
defines	Object		Replace the global variables with the constants defined in the "defines" object.

Example tsconfig.json file:

{
    "compilerOptions": {
        "module": "commonjs",
        "noImplicitAny": true,
        "removeComments": true,
        "preserveConstEnums": true,
        "sourceMap": true,
        "accessorOptimization": true,
        "emitReflection": true,
        "reorderFiles": true
        "defines": {
            "DEBUG": false,
            "RELEASE": true
        }

    },  
    "files": [
        "core.ts",
        "sys.ts"
    ]  
}

Accessor Optimization

Pass --accessorOptimization to the command-line tool or add "accessorOptimization": true to the compilerOptions in tsconfig.json file to enable this feature.

As we know, we can't override the get / set accessors of super class in TypeScript. To solve the problem, we usually forward the call to the set accessor to another method:

TypeScript:

class Student {

    public _name:string;

    protected setName(value:string):void {
        this._name = value;
    }

    public get name():string {
        return this._name;
    }

    public set name(value:string) {
        this.setName(value);
    }
}

It does solve the problem, but also brings a performance issue, that two functions have to be called each time we call a set accessor. With the --accessorOptimization switch on, if the accessor contains only one call to another method, the compiler uses that method to define accessor directly.

Javascript:

var Student = (function () {
    function Student() {
    }
    Student.prototype.setName = function (value) {
        this._name = value;
    };
    Object.defineProperty(Student.prototype, "name", {
        get: function () {
            return this._name;
        },
        set: Student.prototype.setName,
        enumerable: true,
        configurable: true
    });
    return Student;
}());

If you define the setName() method after the set accessor, the final result looks like this:

var Student = (function () {
    function Student() {
    }
    Object.defineProperty(Student.prototype, "name", {
        get: function () {
            return this._name;
        },
        set: setName,
        enumerable: true,
        configurable: true
    });
    Student.prototype.setName = setName;
    function setName(value) {
        this._name = value;
    };
    return Student;
}());

Either way, it works.

Class Reflection

Pass --emitReflection to the command-line tool or add "emitReflection": true to the compilerOptions in tsconfig.json file to enable this feature.

TypeScript:

namespace ts {
    export interface IPerson {
        name:string;
    }
    
    export class Student implements IPerson {
        public name:string = "";
    }
}

JavaScript:

var ts;
(function (ts) {
    var Student = (function () {
        function Student() {
            this.name = "";
        }
        return Student;
    }());
    ts.Student = Student;
    __reflect(Student.prototype, "ts.Student", ["ts.IPerson"]);
})(ts || (ts = {}));

The __reflect helper function is just like the __extends function, it is emitted only once in one file.

Then you can use the helper funtions in reflection.ts to get the qualified class name of an instance:

let student = new ts.Student();
ts.getQualifiedClassName(student);  // "ts.Student"

or do some type checking:

ts.is(student, "ts.Student"); // true
ts.is(student, "ts.IPersion"); // true

SourceFiles Reordering

Pass --reorderFiles to the command-line tool or add "reorderFiles": true to the compilerOptions in tsconfig.json file to enable this feature.

Normally when you pass the --outFile option, the compiler will concatenate and emit output to a single file. But the order of concatenation is determined by the list of files passed to the compiler on the command line (or in the tsconfig.json file) along with triple-slash references and imports. That forces you to sort the input files in the correct order manually. It is ok with only a few source files, but it becomes a disaster when you have countless source files.

With the reorderFiles switch on, the compiler will automatically reorder the source files by analyzing their dependencies in code. Then you can get the correct concatenation order in the generated file without doing any extra effort. I have tested this feature in many real-world projects, it works very well. If it does not work in your project, please feel free to open an issue and send me the test case.

Conditional Compilation

The defines option is only allowed in tsconfig.json, and not through command-line switches.

You can use the defines option to declare global variables that the compiler will assume to be constants (unless defined in scope). Then all the defined global variables will be replaced with the corresponding constants. For example:

tsconfig.json:

{
    "compilerOptions": {
        "defines": {
            "DEBUG": false,
            "LANGUAGE": "en_US"
        }
    }
}

TypeScript:

declare var DEBUG:boolean;
declare var LANGUAGE:string;

if (DEBUG) {
    console.log("DEBUG is true");
}

console.log("The language is : " + LANGUAGE);

function someFunction():void {
    let DEBUG = true;
    if (DEBUG) {
        console.log("DEBUG is true");
    }
}

JavaScript:

if (false) {
    console.log("DEBUG is true");
}

console.log("The language is : " + "en_US");

function someFunction() {
    var DEBUG = true;
    if (DEBUG) {
        console.log("DEBUG is true");
    }
}

As you can see, the second if(DEBUG) in someFunction is not replaced because it is defined in scope.

Note that the compiler does not drop the unreachable code because it is can be easily done by other tools like UglifyJS or Google Closure Compiler.