Better Reusable Media Queries on Emotion

When wanting to use reusable media queries on Emotion you get in the official docs the following example:

/** @jsx jsx */
import { jsx, css } from '@emotion/core'

const breakpoints = [576, 768, 992, 1200]

const mq = breakpoints.map(
  bp => `@media (min-width: ${bp}px)`
)

render(
  <div>
    <div
      css={{
        color: 'green',
        [mq[0]]: {
          color: 'gray'
        },
        [mq[1]]: {
          color: 'hotpink'
        }
      }}
    >
      Some text!
    </div>
    <p
      css={css`
        color: green;
        ${mq[0]} {
          color: gray;
        }
        ${mq[1]} {
          color: hotpink;
        }
      `}
    >
      Some other text!
    </p>
  </div>
)

First you set your breakpoints in an array.

const breakpoints = [576, 768, 992, 1200]

Then you map those values to a string that will have the signature for each of your media queries. This is the piece of code that reusable media queries simplify for you.

const mq = breakpoints.map(
  bp => `@media (min-width: ${bp}px)`
)

Finally you can easily use that media query by just using the mq variable and grabbing the index you want to use.

${mq[0]} {
 color: gray;
}

This is fine but we can do better.

With this approach I found that when setting my media queries they didn't told me about the breakpoint being used. mq[0] is mobile, but what about mq[3]. Is it Ipad, a bigger mobile phone, or desktop?

I needed a way to be more declarative about it. Clearer as to what breakpoint am I using or needing to implement.

So long story short I leave you with the same previous example of reusable media queries but with a new implementation.

/** @jsx jsx */
import { jsx, css } from '@emotion/core'

const bp = {
  small: 500,
  large: 1200
};


const mq = n => {
  const bpArray = Object.keys(bp).map(key => [key, bp[key]]);

  const [result] = bpArray.reduce((acc, [name, size]) => {
    if (n === name) return [...acc, `@media (min-width: ${size}px)`];
    return acc;
  }, []);

  return result;
};



render(
  <div>
    <div
      css={{
        color: 'green',
        [mq('small')]: {
          color: 'gray'
        },
        [mq('large')]: {
          color: 'hotpink'
        }
      }}
    >
      Some text!
    </div>
    <p
      css={css`
        color: green;
        ${mq('small')} {
          color: gray;
        }
        ${mq('large')} {
          color: hotpink;
        }
      `}
    >
      Some other text!
    </p>
  </div>
)

We are now defining breakpoints with an object. We can name our breakpoints with a key and then set the value. It's a plain old object that will give us way better use than the previous array.

const bp = {
  small: 500,
  large: 1200
};

Also note that this time around we can be more flexible about the order too. It won't matter as compared with previous version where changing order in array would mess breakpoint you think you are using but you are not.

const bp = {
  small: 500,
  smaller: 300,
  large: 1200,
  iphone4: 320
};

Next we create a method that will turn the bp object into an array of tuples with name of breakpoint and value of width pairs. Then we will reduce it to get an array with one string that has the signature for the media query you passed as the n argument just like the Emotion docs previous example did.
We finally destructure that array string value into a result variable that we will return.

const mq = n => {
  const bpArray = Object.keys(bp).map(key => [key, bp[key]]);

  const [result] = bpArray.reduce((acc, [name, size]) => {
    if (n === name) return [...acc, `@media (min-width: ${size}px)`];
    return acc;
  }, []);

  return result;
};

So with this config we can now define and call breakpoints by name in a easy and concise way but also explicit about what we are changing.

        ${mq('small')} {
          color: gray;
        }
        ${mq('large')} {
          color: hotpink;
        }

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Better Reusable Media Queries on Emotion

Rodrigo Figueroa

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