I made a terrible thing Sunday night.

The theme that I bought for the new React Indie Bundle page has decorations built with SVG. You slap them into the page as <svg> tags, and it makes your sections look nice.

You’re supposed to slap them into the page as <svg> tags. It’s great that create-react-app has built-in support for importing svgs, right?

Well… that’s meant for images. import arrow from 'decorations/arrow.svg gives you a relative URL. Something like public/decorations/arrow.svg that you’re meant to use as a src prop for an image tag.

import arrow from 'decorations/arrow.svg`
// ...
const Arrow = () =&gt; (
    <img src="{arrow}" />

This, of course, does not work with with the Angle theme. That one wants you to use SVG as a first-class citizen of the DOM. So what’s a guy to do? ?

Well… heh… I built a python script that takes SVG and crudely turns it into a React component. This is a terrible idea, but with a lot of manual massaging, it worked. ?

Here it is:

import os
# from http://stackoverflow.com/questions/4303492/how-can-i-simplify-this-conversion-from-underscore-to-camelcase-in-python
def dash_to_camelcase(value):
    def camelcase():
        yield str.lower
        while True:
            yield str.capitalize
    c = camelcase()
    return "".join(c.next()(x) if x else '-' for x in value.split("-"))
for subdir, dirs, files in os.walk('./top'):
    for file in files:
        path = os.path.join(subdir, file)
        name, ext = file.split('.')
        with open(path, 'r') as f:
            svg = f.read()
            svg = svg.replace('&lt;svg', 'import React from "react"; export const %s = () =&gt; (&lt;svg' % dash_to_camelcase(name), 1) \
                     .replace('class=', 'className=') \
                     .replace('preserveaspectratio=', 'preserveAspectRatio=') \
                     .replace('viewbox=', 'viewBox=') \
                     .replace('stroke-width=', 'strokeWidth=') \
                     .replace('', ')')
            with open(os.path.join(subdir, name+'.js'), 'w') as out:

The script traverses a directory and assumes all the files it finds are SVGs. This is the first red flag. Then it reads the SVG as text and performs some search & replace operations:

  • <svg becomes a React import, and an exported function declaration
  • class, preserveaspectratio, viewbox, and stroke-width are fixed to follow React’s prop naming rules
  • </svg> gets a ) to close the function body.

This is red flag number 2 through 6, maybe 7. Why? Because this is terrible, and I should feel bad. You can’t parse XML with Regex, which this is a simplified instance of, and for the love of god use a parser like lxml.

Several problems showed up:

  • Some files had two <svg> tags. I had to manually edit them every time I re-ran the script because bugs ?
  • Some files had typos in their props, like stroke-width = ". This is valid XML, but my “parser” couldn’t handle it ➡ manual edits
  • Files with two <svg>s have to be wrapped in a <div> to fulfill React’s “one child per component” policy. This needs manual edits because my “parser” knows nothing.

2 hours after I started, I was done. Happy to have successfully turned 30 svgs into React components, I could now use the two that I needed. Excellent.

Yak shaving at its finest.

This could make a useful Webpack plugin, though. Import SVG as a React component? That sounds like something everybody needs ?

Learned something new? 💌

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