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How to set a variable not equal to any value in SASS?
- 王林forward
- 2023-08-31 09:01:071014browse
SASS, or Syntactically Awesome Style Sheets, is a very popular preprocessor scripting language among developers, used to enhance the functionality of CSS. SASS allows developers to use variables, nesting, mixins, and other advanced features not available in CSS.
One of the key features of using SASS is the ability to declare variables, which are nothing more than placeholders for values that we can reuse throughout our web application stylesheets. Variables help save developers time and effort by allowing them to update multiple values at once by making the code more readable and easier to maintain.
Sometimes, we may want to set a variable to empty, which in other languages means setting the variable to null or undefined. This is useful when we want to create a placeholder variable and can assign a value to it later in the application. In this article, we will learn how to set a variable not equal to anything in SASS.
prerequisites
To run SASS in HTML, make sure you have the SASS compiler installed in your IDE (just like in VS Code), download and install the SASS compiler using the following command -
npm install -g sass
This will install the SASS compiler globally on your system. Next, create a new file with a .scss extension that will contain our SASS code.
After that, import the SASS file into the HTML file. In the HTML file, add a link to your SASS file using the 'link' tag in the head section. The link's rel attribute should be set to "stylesheet" and its href attribute should be set to the path to your SASS file.
Different ways to set a variable to not be equal to anything in SASS
To set a variable not equal to any value, there are several ways, such as using the null keyword, the unset function, or the #{} interpolation method. Let us discuss all these methods in detail one by one.
Method 1: Use Null keyword
In SASS, the null keyword is used to indicate the absence of a value. When a variable is set to null, it means that the variable has not been assigned any value. This is useful when you want to declare a variable but don't want to assign a value to it immediately.
grammar
To set a variable to not be equal to anything in SASS, just use the null keyword as shown below -
$newVar: null;
Alternatively, we can set a variable to null by assigning it to a variable that has already been set to null
$newOtherVar: $newVar;
Example
Let’s see a complete example of how to set a variable to nothing using null keyword.
HTML code
<!DOCTYPE html>
<html>
<head>
<title>Example to set the variable to equal nothing using null keyword</title>
<style>
/* Add the CSS compiled code below */
</style>
</head>
<body>
<h1>Welcome to Tutorialspoint!</h1>
<p>The one stop solution to learn technology articles.</p>
</body>
</html>
SASS code
Below is the SASS code where we declare the variable $newVar with a value equal to null.
$newVar: null;
body {
background-color: $newVar;
color: $newVar;
font-size: $newVar;
}
Compiled CSS code
The following is the compiled code generated after compiling the above SASS code with the help of the SASS compiler. To see the changes in the document, make sure to add the following code between the
body {
background-color: ;
color: ;
font-size: ;
}
Method 2: Use the Unset function
Another way to set a variable to empty in SASS is to use the unset function. The unset function removes a variable from memory, effectively setting it to null. Here is an example of how to set a variable to null using the unset function.
grammar
$newVar: 15; $newVar: unset($newVar);
In the above syntax, $newVar is first assigned a value of 15. Then use the unset function to remove $newVar from memory, effectively setting it to null.
Example
Let’s see a complete example of how to set a variable to None using the unset function.
HTML code
<!DOCTYPE html>
<html>
<head>
<title>Example to set the variable to equal nothing using unset function</title>
<style>
/* Add the CSS compiled code below */
</style>
</head>
<body>
<h1>Welcome to Tutorialspoint!</h1>
<p>The one stop solution to learn technology articles.</p>
</body>
</html>
SASS code
The following is the SASS code, in which we declare two variables $newVar1 and $newVar2, whose values are equal to 15 and 12 respectively. Now, the unset function is used to remove $newVar1 and $newVar2 from memory, effectively setting them to null.
$newVar1: 15;
$newVar1: 12;
$newVar1: unset($newVar1);
$newVar2: unset($newVar2);
h1 {
font-size: $newVar1;
}
p {
font-size: $newVar2;
}
Compiled CSS code
The following is the compiled code generated after compiling the above SASS code with the help of the SASS compiler. To see the changes in the document, make sure to add the following code between the
h1 {
font-size: ;
}
p {
font-size: ;
}
Method 3: Use #{} interpolation
The #{} interpolation syntax is evaluated at compile time, so in compiled CSS, the resulting value of $newVar will be the empty string. This may not be desired behavior in some situations, so use this technique with caution when appropriate.
grammar
$newVar: #{" "};
In the above syntax, $newVar is set to an empty string, which is created using #{} interpolation syntax with a space inside. This technique is useful when you need to set a variable to an empty string instead of null.
Example
Let's look at an example of setting a variable to None using the interpolation method.
HTML code
<!DOCTYPE html>
<html>
<head>
<title>Example to set the variable to equal nothing using Interpolation</title>
<style>
/* Add the CSS compiled code below */
</style>
</head>
<body>
<h1>Welcome to Tutorialspoint!</h1>
</body>
</html>
SASS code
Below is the SASS code where we declare a variable $newVar and set it to the empty string using interpolation syntax.
$newVar: #{" "};
body {
padding: $newVar;
margin: $newVar;
}
编译的 CSS 代码
下面是在 SASS 编译器的帮助下编译上述 SASS 代码后生成的编译代码。要查看文档中的更改，请确保在相应 HTML 文件中的
body {
padding: ;
margin: ;
}
结论
在本文中，我们了解了如何使用不同的方法在 SASS 中将变量设置为空，包括使用 null 关键字、unset 函数和 #{} 插值语法。详细介绍这些技术，它们在不同情况或项目需求中非常有用，在这些情况或项目需求中，我们需要创建一个占位符变量，稍后可以在应用程序中为其分配值。
在SASS中，声明变量更具可读性和可维护性，从而节省了开发人员的时间和精力。要使用 SASS，请确保在 IDE 中安装了 SASS 编译器，就像上面讨论的在 VS Code 中使用 SASS 的过程一样，我们需要将 SASS 文件正确导入到 HTML 文件中。
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