Commit cf2f9267 authored by Mike Bostock's avatar Mike Bostock
Browse files

Update CHANGES.

parent 1c692fcc
# Changes in D3 4.0
D3 3.x was a monolithic library: the core functionality resided in a single [repository](https://github.com/d3/d3) and was published in a [single file](https://d3js.org/d3.v3.js). It was possible to create a custom build using a [nonstandard tool](https://github.com/mbostock/smash), but not easy and few did. (There were also plugins, but these could only add features and had their own [monolithic repository](https://github.com/d3/d3-plugins).)
D3 3.x was a monolithic library: the core functionality resided in a single repository and was published in a single file, d3.v3.js. It was possible to create a custom build using a [nonstandard tool](https://github.com/mbostock/smash), but not easy and few did. (There were also plugins, but these could only add features and had their own [monolithic repository](https://github.com/d3/d3-plugins).)
D3 4.0 is modular. Instead of one library, D3 is now [many small libraries](https://github.com/d3) that are designed to work together. You can pick and choose which parts to use as you see fit. Each library is maintained in a separate repository, allowing decentralized ownership and independent release cycles. Want to own a new repository in the [D3 organization](https://github.com/d3)? [Let me know!](https://twitter.com/mbostock)
D3 4.0 is modular. Instead of one library, D3 is now [many small libraries](#table-of-contents) that are designed to work together. You can pick and choose which parts to use as you see fit. Each library is maintained in its own repository, allowing decentralized ownership and independent release cycles. Want to own a new repository in the [D3 organization](https://github.com/d3)? [Let me know!](https://twitter.com/mbostock)
The [default bundle](https://d3js.org/d3.v4.0.0-alpha.50.js) of D3 4.0 conveniently aggregates [about thirty](https://github.com/d3/d3/blob/master/index.js) of these microlibraries.
The default bundle of D3 4.0 conveniently aggregates about thirty of these microlibraries.
```html
<script src="https://d3js.org/d3.v4.0.0-alpha.50.min.js"></script>
......@@ -17,21 +17,23 @@ As before, you can load optional plugins on top of the default bundle, such as [
<script src="https://d3js.org/d3-scale-chromatic.v0.3.min.js"></script>
```
But now in 4.0, you don’t have to use the default bundle! Custom bundles are useful for applications that use a subset of D3’s features; for example, a React charting library might use D3’s scales and shapes, but use React instead of selections to manipulate the DOM. Or if you’re just using [d3-selection](https://github.com/d3/d3-selection), it’s only 5KB instead of 64KB for the default bundle. You can load D3 microlibraries using vanilla script tags or RequireJS (great for HTTP/2!):
4.0 no longer requires you to use the default bundle! Custom bundles are great for applications that use a subset of D3’s features; for example, a React chart library might use D3 for scales and shapes, and React to manipulate the DOM. Or if you’re just using [d3-selection](https://github.com/d3/d3-selection), load it directly. You can load D3 microlibraries using vanilla script tags or RequireJS (great for HTTP/2!):
```html
<script src="https://d3js.org/d3-selection.v0.9.min.js"></script>
```
You can `cat` D3 microlibraries into a custom bundle, or use tools such as [Webpack](https://webpack.github.io/) or [Rollup](http://rollupjs.org/) to create [optimized bundles](https://bl.ocks.org/mbostock/bb09af4c39c79cffcde4). The D3 microlibraries are written as [ES6 modules](http://www.2ality.com/2014/09/es6-modules-final.html), and Rollup lets you pick at the symbol level to produce the smallest bundles!
You can `cat` D3 microlibraries into a custom bundle, or use tools such as [Webpack](https://webpack.github.io/) and [Rollup](http://rollupjs.org/) to create [optimized bundles](https://bl.ocks.org/mbostock/bb09af4c39c79cffcde4). The D3 microlibraries are written as [ES6 modules](http://www.2ality.com/2014/09/es6-modules-final.html), and Rollup lets you pick at the symbol level to produce smaller bundles.
Small files are nice, but modularity is also about making D3 *fun* again. Microlibraries are easier to understand, develop and test. They make it easier for new people to get involved and contribute. They reduce the distinction between a “core module” and a “plugin”, and increase the pace of development in D3 features.
If you don’t care about modularity, you can mostly ignore this change and keep using the default bundle. However, there’s an unavoidable consequence of adopting ES6 modules: every symbol in D3 4.0 now shares a flat namespace rather than the nested one of D3 3.x. For example, d3.scale.linear is now d3.scaleLinear, and d3.layout.treemap is now d3.treemap. The adoption of ES6 modules also means that D3 is now written exclusively in [strict mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode) and has better readability. And there have been many other significant improvements to D3’s features! (Nearly all of the code from D3 3.x has been rewritten.) These changes are covered in the sections below.
If you don’t care about modularity, you can mostly ignore this change and keep using the default bundle. However, there’s an unavoidable consequence of adopting ES6 modules: every symbol in D3 4.0 now shares a flat namespace rather than the nested one of D3 3.x. For example, d3.scale.linear is now d3.scaleLinear, and d3.layout.treemap is now d3.treemap. The adoption of ES6 modules also means that D3 is now written exclusively in [strict mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode) and has better readability. And there have been many other significant improvements to D3’s features! (Nearly all of the code from D3 3.x has been rewritten.) These changes are covered below.
The default D3 [UMD bundle](https://github.com/umdjs/umd) is now [anonymous](https://github.com/requirejs/requirejs/wiki/Updating-existing-libraries#register-as-an-anonymous-module-), rather being named “d3”. No `d3` global is exported if AMD or CommonJS is detected. In a vanilla environment, the D3 microlibraries share the `d3` global, meaning the code you write for the default D3 bundle works identically if you load the modules separately. (See [Let’s Make a (D3) Plugin](https://bost.ocks.org/mike/d3-plugin/) for more.) The generated UMD bundles are no longer stored in the Git repository; Bower has been repointed to [d3-bower](https://github.com/mbostock-bower/d3-bower), and you can find the generated files on [npmcdn](https://npmcdn.com/d3@next/) or attached to the [latest release](https://github.com/d3/d3/releases/latest). The non-minified default bundle is no longer mangled, making it more readable and preserving inline comments.
### Other Global Changes
To the consternation of some users, D3 3.x employed Unicode variable names such as τ and π for a concise representation of mathematical operations. A downside of this approach was that a SyntaxError would occur if you loaded the non-minified D3 using ISO-8859-1 instead of UTF-8. D3 3.x also used Unicode string literals, such as the SI-prefix µ for 1e-6. D3 4.0 uses only ASCII variable names and ASCII string literals (see [rollup-plugin-ascii](https://github.com/mbostock/rollup-plugin-ascii)), avoiding these encoding problems.
The default [UMD bundle](https://github.com/umdjs/umd) is now [anonymous](https://github.com/requirejs/requirejs/wiki/Updating-existing-libraries#register-as-an-anonymous-module-), rather being named “d3”. No `d3` global is exported if AMD or CommonJS is detected. In a vanilla environment, the D3 microlibraries share the `d3` global, meaning the code you write for the default D3 bundle works identically if you load the modules separately. (See [Let’s Make a (D3) Plugin](https://bost.ocks.org/mike/d3-plugin/) for more.) The generated UMD bundles are no longer stored in the Git repository; Bower has been repointed to [d3-bower](https://github.com/mbostock-bower/d3-bower), and you can find the generated files on [npmcdn](https://npmcdn.com/d3@next/) or attached to the [latest release](https://github.com/d3/d3/releases/latest). The non-minified default bundle is no longer mangled, making it more readable and preserving inline comments.
To the consternation of some users, D3 3.x employed Unicode variable names such as λ, φ, τ and π for a concise representation of mathematical operations. A downside of this approach was that a SyntaxError would occur if you loaded the non-minified D3 using ISO-8859-1 instead of UTF-8. D3 3.x also used Unicode string literals, such as the SI-prefix µ for 1e-6. D3 4.0 uses only ASCII variable names and ASCII string literals (see [rollup-plugin-ascii](https://github.com/mbostock/rollup-plugin-ascii)), avoiding encoding problems.
### Table of Contents
......
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