检查是否在SASS中定义了变量

Just as a complementary answer - you should have a look on the default keyword for certain use cases. It gives you the possibility to assign a default value to variables in case they are not defined yet.

You can assign to variables if they aren’t already assigned by adding the !default flag to the end of the value. This means that if the variable has already been assigned to, it won’t be re-assigned, but if it doesn’t have a value yet, it will be given one.

Example:

In specific-variables.scss you have:

$brand: "My Awesome Brand";

In default-variables.scss you have:

$brand: company-name !default;
$brand-color: #0074BE !default;

Your project is built like this:

@import "specific-variables.scss"; @import "default-variables.scss"; @import "style.scss";

The value of brand will be My Awesome Brand and the value of brand color will be #0074BE.