Introduction to methods of using less (variables, mixing, matching, operations, nesting)

How to use less and some commonly used ones (Variables, mixing, matching, operations, nesting)

Less introduction and compilation tools

What is less

1.LESSCSS is a dynamic style language and a type of CSS preprocessing language. It uses a syntax similar to CSS and gives CSS the characteristics of a dynamic language, such as variables and inheritance, operations, functions, etc., make it easier to write and maintain CSS.
LESSCSS can be used in multiple languages ​​and environments, including browsers, desktop clients, and servers.

less's compilation tool

1. Koala Koala--if there is no CSS folder created during compilation, Koala will automatically generate one for you
   How to set the language
   
   How to compile
   -

2. Let webstorm support less compilation:

• Installationnode.js --- This is a package management tool that will be used in the future

• WIN+ R

• Enter npm install less

....

less Grammar

Ps: The following knowledge points will use the above knowledge points (for example, variables will be used in mixing to deepen the impression^_^)

1. Comments

• // Only displayed in less
  

• /**/ Will be compiled during compilation A good css file shows the writing method of

variable

• ##less

  @ly_width:100px;
  .box {
  width:@ly_width;
  }

• What is displayed in css after compilation is

  .box {
  width:100px;
  }

• define variables with @

Mix

• Solve the border-radius compatibility

  .border_radius (@radius: 5px) {
  -webkit-border-radius: @radius;
  -moz-border-radius: @radius;
  -ms-border-radius: @radius;
  -o-border-radius: @radius;
  border-radius: @radius;
  }

• less writing method

  @ly_width:100px;
  @ly_height:200px;
  @ly_color:green;
  .border(@border_width:3px;) {
  border:@border_width solid red;
  }
  .one {
  width:@ly_width;
  height:@ly_height;
  background-color:@ly_color;
  .border();
  }

• After compilation, what is displayed in css is the writing method in

  .one {
  width: 100px;
  height: 200px;
  background-color: #008000;
  border: 3px solid #ff0000;
  }

##less

• @ly_width:100px;
  @ly_height:200px;
  @ly_color:green;
  .border(@border_width) {
  border:@border_width solid red;
  }
  .one {
  width:@ly_width;
  height:@ly_height;
  background-color:@ly_color;
  .border(1px);
  }

What is displayed in the css after compilation is

• .one {
  width: 100px;
  height: 200px;
  background-color: #008000;
  border: 1px solid #ff0000;
  }

First, upload the code in less. What if you want to apply the .border style in .one?

• @ly_width:100px;
  @ly_height:200px;
  @ly_color:green;
  .border {
  border:1px solid red;
  }
  .one {
  width:@ly_width;
  height:@ly_height;
  background-color:@ly_color;
  }

Write as follows

• @ly_width:100px;
  @ly_height:200px;
  @ly_color:green;
  .border {
  border:1px solid red;
  }
  .one {
  width:@ly_width;
  height:@ly_height;
  background-color:@ly_color;
  .border;
  }

After compilation, what is displayed in css is

• .border { border:1px solid red ; } .one { width: 100px; height: 200px; background-color: #008000; border: 1px solid red; }
  

without Mixing of parameters
Mixing with parameters---without default value (You can pass multiple parameters, separated by commas or semicolons. It is recommended to use semicolons. The following parameters are Example)
Mixing with parameters---with default value (multiple parameters can be passed, below is one parameter as an example)
In When solving css3 compatibility, we often use the

matching pattern

less writing method

• //定义上,下,左,右边框的样式
  .border(top;@border_width:5px;@border_color:red){
  border-top:@border_width solid @border_color;
  }
  .border(bottom;@border_width:5px;@border_color:red){
  border-bottom:@border_width solid @border_color;
  }
  .border(left;@border_width:5px;@border_color:red){
  border-left:@border_width solid @border_color;
  }
  .border(right;@border_width:5px;@border_color:red){
  border-right:@border_width solid @border_color;
  }
  //如果想写通用的样式 可以在下面的代码中写 格式是固定的 
  .border(@_,@border_width:5px;@border_color:red){
  border-color:yellow;
  }
  .border_use1 {
  //选择和if差不多 如果是left就调用上面对应的
  .border(left);
  }
  .border_use2 {
  //选择和if差不多 如果是right就调用上面对应的
  .border(right);
  }

What is displayed in the css after compilation is

• .border_use1 {
  border-left:5px solid #ff0000;
  border-color:yellow;
  }
  .border_use2 {
  border-right:5px solid #ff0000;
  border-color:yellow;
  }

can be understood as if is somewhat similar to the above mix

Operation

How to write in less

• @ly_width:100px;
  .one {
  width:@ly_widht + 100;
  }

What is displayed in css after compilation

• .one {
  width:200px;
  }

Operations provide addition, subtraction, multiplication, and division operations, and can also perform operations on attribute values ​​and colors...

Nesting

##html structure

<p>
</p><p></p>

Writing in less

@ly_width:100px;
@ly_height:200px;
@ly_color:red;
.one {
width:@ly_width;
height:@ly_height;
background-color:@ly_color;
.two {
    background-color: green;
}
}

What is displayed in css after compilation is

.one {
width: 100px;
height: 200px;
background-color: #ff0000;
}
.one .two {
  background-color: green;
}

You can nest another selector in a selector, the code looks like Clear hierarchy to improve code maintainability

• ##@arguments variable

How to write in less

//和前面提到的混合一起举个栗子  
.border(@border_width;@border_style;@border_color){
border:@arguments;
}
.one {
.border(1px;solid;red);
}

• What is displayed in the css after compilation is

  .one {
  border:1px solid #ff0000;
  }

• ##can include all variables and process the variables together

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