How to Implement @for Loops in Styled-Components for Dynamic CSS

How to Implement @for Loops in Styled-Components for Dynamic CSS

Styled-components do not natively support SCSS-like @for loops, but you can achieve similar functionality using JavaScript. Below, we'll show how to dynamically generate styles using a loop in JavaScript.

SCSS Approach

In SCSS, you might write:

@for $i from 0 through 20 {
  #loadingCheckCircleSVG-#{$i} {
    animation: fill-to-white 5000ms;
    animation-delay: ($i - 1.5) * 1s;
    fill: white;
    opacity: 0;
  }
}

Equivalent Styled-Components Solution

Since styled-components allows JavaScript interpolations, we can achieve the same effect using a function that generates CSS dynamically:

import styled, { css } from 'styled-components'

function createCSS() {
  let styles = ''

  for (let i = 0; i <= 20; i++) {
    styles += `
       #loadingCheckCircleSVG-${i} {
         animation: fill-to-white 5000ms;
         animation-delay: ${i - 1.5}s;
         fill: white;
         opacity: 0;
       }
     `
  }

  return css`
    ${styles}
  `
}

const StyledWrapper = styled.div`
  ${createCSS()};
`

Passing Props to Dynamic Styles

If you need to pass props to customize the loop, update the function like this:

function createCSS(count: number) {
  let styles = ''

  for (let i = 0; i <= count; i++) {
    styles += `
       #loadingCheckCircleSVG-${i} {
         animation: fill-to-white 5000ms;
         animation-delay: ${i - 1.5}s;
         fill: white;
         opacity: 0;
       }
     `
  }

  return css`
    ${styles}
  `
}

const StyledWrapper = styled.div<{ count: number }>`
  ${({ count }) => createCSS(count)};
`

Key Takeaways

✅ Use JavaScript loops to generate styles dynamically

✅ Use the css helper for interpolations in styled-components

✅ Pass props to modify the number of generated styles dynamically

FAQs

1. Why doesn't styled-components support SCSS @for loops?

Styled-components is built using JavaScript, and SCSS syntax is not supported. Instead, JavaScript loops can be used to generate similar styles dynamically.

2. What if I need to conditionally apply styles based on props?

You can modify createCSS to accept props and generate styles dynamically based on those props.

3. Does this approach affect performance?

As long as loops are not generating a large number of styles, the impact on performance is minimal.

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Let me know if you need further refinements! 🚀