Angular Build Optimizer

Angular Build Optimizer contains Angular optimizations applicable to JavaScript code as a TypeScript transform pipeline.

# Available optimizations

Transformations applied depend on file content:

- Class fold, Scrub file and Prefix functions: applied to Angular apps and libraries.
- Import tslib: applied when TypeScript helpers are found.

Some of these optimizations add `/*@__PURE__*/` comments. These are used by JS optimization tools to identify pure functions that can potentially be dropped.

## Class fold

Static properties are folded into ES5 classes:

// input
var Clazz = (function () { function Clazz() { } return Clazz; }());
Clazz.prop = 1;
// output
var Clazz = (function () { function Clazz() { } Clazz.prop = 1; return Clazz; }());

## Scrub file

Angular decorators, property decorators and constructor parameters are removed, while leaving non-Angular ones intact.

// input
import { Injectable, Input, Component } from '@angular/core';
import { NotInjectable, NotComponent, NotInput } from 'another-lib';
var Clazz = (function () { function Clazz() { } return Clazz; }());
Clazz.decorators = [{ type: Injectable }, { type: NotInjectable }];
Clazz.propDecorators = { 'ngIf': [{ type: Input }] };
Clazz.ctorParameters = function () { return [{type: Injector}]; };
var ComponentClazz = (function () {
function ComponentClazz() { }
__decorate([
Input(),
__metadata("design:type", Object)
], Clazz.prototype, "selected", void 0);
__decorate([
NotInput(),
__metadata("design:type", Object)
], Clazz.prototype, "notSelected", void 0);
ComponentClazz = __decorate([
NotComponent(),
Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
], ComponentClazz);
return ComponentClazz;
}());
// output
import { Injectable, Input, Component } from '@angular/core';
import { NotInjectable, NotComponent } from 'another-lib';
var Clazz = (function () { function Clazz() { } return Clazz; }());
Clazz.decorators = [{ type: NotInjectable }];
var ComponentClazz = (function () {
function ComponentClazz() { }
__decorate([
NotInput(),
__metadata("design:type", Object)
], Clazz.prototype, "notSelected", void 0);
ComponentClazz = __decorate([
NotComponent()
], ComponentClazz);
return ComponentClazz;
}());

## Prefix functions

Adds `/*@__PURE__*/` comments to top level downleveled class declarations and instantiation.

Warning: this transform assumes the file is a pure module. It should not be used with unpure modules.

// input
var Clazz = (function () { function Clazz() { } return Clazz; }());
var newClazz = new Clazz();
var newClazzTwo = Clazz();
// output
var Clazz = /*@__PURE__*/ (function () { function Clazz() { } return Clazz; }());
var newClazz = /*@__PURE__*/ new Clazz();
var newClazzTwo = /*@__PURE__*/ Clazz();

## Prefix Classes

Adds `/*@__PURE__*/` to downleveled TypeScript classes.

// input
var ReplayEvent = (function () {
function ReplayEvent(time, value) {
this.time = time;
this.value = value;
}
return ReplayEvent;
}());
// output
var ReplayEvent = /*@__PURE__*/ (function () {
function ReplayEvent(time, value) {
this.time = time;
this.value = value;
}
return ReplayEvent;
}());

## Import tslib

TypeScript helpers (`__extends/__decorate/__metadata/__param`) are replaced with `tslib` imports whenever found.

// input
var __extends = (this && this.__extends) || function (d, b) {
for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
function __() { this.constructor = d; }
d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
// output
import { __extends } from "tslib";

## Wrap enums

Wrap downleveled TypeScript enums in a function, and adds `/*@__PURE__*/` comment.

// input
var ChangeDetectionStrategy;
(function (ChangeDetectionStrategy) {
ChangeDetectionStrategy[ChangeDetectionStrategy["OnPush"] = 0] = "OnPush";
ChangeDetectionStrategy[ChangeDetectionStrategy["Default"] = 1] = "Default";
})(ChangeDetectionStrategy || (ChangeDetectionStrategy = {}));
// output
var ChangeDetectionStrategy = /*@__PURE__*/ (function () {
var ChangeDetectionStrategy = {};
ChangeDetectionStrategy[ChangeDetectionStrategy["OnPush"] = 0] = "OnPush";
ChangeDetectionStrategy[ChangeDetectionStrategy["Default"] = 1] = "Default";
return ChangeDetectionStrategy;
})();

# Library Usage

import { buildOptimizer } from '@angular-devkit/build-optimizer';
const transpiledContent = buildOptimizer({ content: input }).content;

Available options:

export interface BuildOptimizerOptions {
content?: string;
inputFilePath?: string;
outputFilePath?: string;
emitSourceMap?: boolean;
strict?: boolean;
isSideEffectFree?: boolean;
}

# Webpack loader usage:

import { BuildOptimizerWebpackPlugin } from '@angular-devkit/build-optimizer';
module.exports = {
plugins: [
new BuildOptimizerWebpackPlugin(),
]
module: {
rules: [
{
test: /\.js$/,
loader: '@angular-devkit/build-optimizer/webpack-loader',
options: {
sourceMap: false
}
}
]
}
}

# CLI usage

build-optimizer input.js
build-optimizer input.js output.js