Handling Errors in SASS/SCSS with @error

1. Introduction

In this tutorial, we will focus on handling errors in SASS/SCSS with the @error directive. This powerful feature allows us to generate custom error messages, which can significantly improve code quality and debugging processes.

By the end of this tutorial, you will be able to:

• Understand the purpose of the @error directive in SASS/SCSS.
• Create custom error messages.
• Implement error handling in your SASS/SCSS code.

Prerequisites

A basic understanding of SASS/SCSS is required. Familiarity with CSS and basic programming concepts like variables, functions, and control flow will be helpful.

2. Step-by-Step Guide

The @error directive throws an error with a custom message. The message can include SASS script, such as variables. This can be particularly useful in mixins and functions where certain conditions must be met.

Here is a simple example:

@function divide($a, $b) {
  @if $b == 0 {
    @error "division by zero is undefined";
  }
  @return $a / $b;
}

In the above example, an error message "division by zero is undefined" is thrown if the second parameter is zero.

3. Code Examples

Example 1:

@function divide($a, $b) {
  @if $b == 0 {
    @error "division by zero is undefined";
  }
  @return $a / $b;
}

.result {
  width: divide(10, 2);  // No error, result is 5
  height: divide(10, 0); // Error: division by zero is undefined
}

In this example, the divide function is used to divide two numbers. If the second number is zero, an error message is thrown. The .result class will have a width of 5, but the height will throw an error, stopping the CSS from being generated.

4. Summary

This tutorial covered the @error directive in SASS/SCSS, which allows you to throw custom error messages. This is a very powerful tool for debugging and improving your code quality.

Next steps for learning would be to explore other SASS/SCSS directives such as @warn and @debug. More information on these directives can be found in the SASS/SCSS documentation.

5. Practice Exercises

Exercise 1: Write a function that calculates the square root of a number. If the input is a negative number, it should throw an error.

Solution:

@function sqrt($num) {
  @if $num < 0 {
    @error "Can't find the square root of a negative number";
  }
  @return sqrt($num);
}

.my-class {
  width: sqrt(16);  // No error, result is 4
  height: sqrt(-4); // Error: Can't find the square root of a negative number
}

Exercise 2: Write a mixin that applies a border to an element. The mixin should accept two arguments: the border-width and the border-color. If the border-width is not a number or the border-color is not a color, it should throw an error.

Solution:

@mixin border($width, $color) {
  @if type-of($width) != number {
    @error "Border width must be a number";
  }
  @if type-of($color) != color {
    @error "Border color must be a color";
  }
  border: $width solid $color;
}

.my-class {
  @include border(2, red);   // No error
  @include border("2", red); // Error: Border width must be a number
}