A detailed explanation of the differences between CSS syntax and JSON and JS objects

JSON objects are subclasses of JS objects, and CSS objects are subclasses of JSON, that is, CSS inherits JS objects. This article mainly introduces the differences between CSS syntax and JSON and JS objects in detail. Friends who are interested should take a look at it. I hope it can help you.

CSS (Cascading Style Sheets) rules consist of 2 parts: selector and declaration.　　

selector｛declaration1;declaration2;declaration3;...declarationN｝

Declaration is separated by semicolons (;) and expressed as property:value1 value2.. It is a single-layer structure without inner nesting.

Value is a specific value such as px for size, #FFFFFF for color, relative/absolute for position, etc.

The selector can be represented by multiple selectors separated by commas, such as h1,h2,h3,h4..

Note: Code CSS should pay attention to whether the attribute values ​​​​are required to be in order or not

　backgroud: color position size repeat attachment url("img .url")When the browser renders and parses this type of attribute, it can modify the specified attribute by using regular rules to determine the type of value. The order and value type can be matched at will.

　Padding: Left top right bottom Such attributes are parsed in order when they are rendered. If you want to modify the specified attribute, you need to complete its previous value.

JSON (Javascript Object Nonation) consists of object declarations.

　{declaration1,declaration2,..declarationN}

Its representation can be a tree-like multi-level nested structure, and the properties of the object can be represented by another or multiple objects. The outer layer of multiple objects is closed by the JS array [] symbol, the object is closed by the collection symbol {}, and a colon is used to indicate the mapping relationship.

JS object

It is composed of the collection symbol {}, and the content is attributes: values, separated by commas. The structure is similar to the JSON object and can be nested, but its attributes It does not have to be enclosed in quotation marks.

To sum up, it can be concluded that JSON objects are subclasses of JS objects, and CSS objects are subclasses of JSON, that is, CSS inherits JS objects.

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