CSS | compare() Function

The CSS compare() function allows you to compare two values and returns a value of "less than", "equal to" or "greater than". This function is useful in conditional statements and sorting algorithms.

Syntax

compare(value1, value2)

• value1 - the first value to compare
• value2 - the second value to compare

Return Values

The compare() function returns one of three values:

• -1 - if value1 is less than value2
• 0 - if value1 is equal to value2
• 1 - if value1 is greater than value2

Example

Let's say we have two variables defined in CSS:

:root {
  --my-color1: #333;
  --my-color2: #666;
}

We can use the compare() function to compare these two variables and output the result:

.example {
  content: 'my-color1 is ' compare(var(--my-color1), var(--my-color2)) ' than my-color2';
}

This will output:

my-color1 is -1 than my-color2

Conditional Statements

We can also use the compare() function in conditional statements. For example:

.example {
  font-size: 20px;
  color: var(--my-color1);
  
  @if compare(var(--my-color1), var(--my-color2)) = -1 {
    color: var(--my-color2);
  }
}

This will change the color of .example to var(--my-color2) if var(--my-color1) is less than var(--my-color2).

Sorting Algorithms

The compare() function is especially useful in sorting algorithms. For example:

.my-list > li {
  list-style: none;
  font-size: 18px;
}

.my-list > li:nth-child(2n) {
  color: red;
}

.my-list > li:nth-child(2n+1) {
  color: blue;
}

.my-list {
  display: flex;
  flex-direction: column;
  
  &.sort-by-value {
    .my-list > li {
      order: compare(get-value-of-li($a), get-value-of-li($b));
    }
  }
}

This will sort the list items in ascending order based on their values. In this case, get-value-of-li() is a custom function that extracts the value from each list item.

Conclusion

The compare() function is a powerful tool for conditionally styling elements and sorting data in CSS. It can be used in a variety of scenarios and is available in most modern browsers.