Think carbon, reduce typescript bundle size
📅 Published: • Thomas Queste
Reducing the size of JS compiled from Typescript is easy.
Here are some numbers and how to do it. It’s nearly free if you run on Node (!= browser).
TL;DR
- Install
tslib - Configure
importHelpers
= reduce JS file size = reduce storage and network = 🌿 Reduce carbon footprint!
Size matters
Sizes after and before, with the difference in percent:
| Before | After | Diff | |
|---|---|---|---|
| line count *.js | 4397 lines | 4011 lines | -9% |
| size in bytes *.js | 186k | 153k | -18% |
How-to
Install tslib, the library that contains the helper code:
npm install tslib
Enable the import of the helper functions:
{
"compilerOptions": {
"importHelpers": true
}
}
What does it do
Typescript will create helper functions for decorators, extends, assign, etc. in each compiled file.
But, Typescript can use a reference library, tslib and import the functions from there.
Sample of generated code without tslib/importHelpers:
var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
return c > 3 && r && Object.defineProperty(target, key, r), r;
};
With tslib/importHelpers:
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
const tslib_1 = require("tslib");
Measuring
I measured the size before and after with the following commands:
# don't forget to do a clean-build
# npm run clean && npm run build
# count lines
( find ./dist -name '*.js' -print0 | xargs -0 cat ) | wc -l
# total size in bytes
{ find dist -type f -name "*.js" -printf "%s+"; echo 0; } | bc