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Introduction to yaml Basics
2021-08-27 08:41:50 【coderwxf】
This is my participation 8 The fourth of the yuegengwen challenge 23 God , Check out the activity details :8 Yuegengwen challenge
YAML It's a kind of more humanized Data serialization language , It can be used with most current programming languages .
YAML Its grammar is simple and intuitive , The feature is to use indentation to express the hierarchy
YAML Most of them are used in Writing configuration files , As a general document .yml or .yaml
For the suffix
Writing rules
- Case sensitive
# The following two are different
name: klaus
Name: klaus
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- Use indentation to indicate hierarchy
- Indentation is not allowed Tab key , Only Spaces are allowed .
- The number of Spaces indented is not important , As long as the elements of the same level are aligned to the left
# YAML
info:
name: klaus
firend:
name: Alex
age: 18
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- Use
#
Notation ,-
From this character to the end of the line , Will be ignored by the parser
-
That is to say
yaml
Only single line comments are supported
-
# I am a comment
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- Support streaming style ( Flow style) The grammar of ( Wrap it in curly brackets , Separate with a comma and a space , similar JSON)
- That is to say
yaml
Files are native and can support json Format
# yaml It can be parsed normally json Content of format
{
"name": "Klaus",
"age": 23
}
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We can this Test platform see yaml Compiled into js The result of the object or Use this Test platform see yaml Compiled as json Result
object
# object --- Add a space after the colon
# Object key value pairs are represented by colons key: value,
# key: value
name: Klaus # => { name: 'Klaus' }
# ----------------------------------
# Object nesting
# How to write it 1
info :
name: Klaus
# => { info: { name: 'Klaus' } }
# How to write it 2
# Support streaming style
info : { name: Klaus } # => { info: { name: 'Klaus' } }
info: {
name: Klaus,
age: 23
}
# => { info: { name: 'Klaus', age: 23 } }
# How to write it 4 --- The question mark plus a space represents a complex key
?
- complexkey1
- complexkey2
:
- complexvalue1
- complexvalue2
# => 'complexkey1,complexkey2': [ 'complexvalue1', 'complexvalue2' ] }
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Array
# Array
# A group in block format (Block Format)( namely “ Dashes + Space ”) The first data forms an array
- Cat
- Dog
- Fish
# => [ 'Cat', 'Dog', 'Fish' ]
-
- Cat
- Dog
- Fish
# => [ [ 'Cat', 'Dog', 'Fish' ] ]
# Inline format is supported (Inline Format) To express ( Wrap... In square brackets , Comma with space , similar JSON)
[ Cat, Dog, Fish ] # => [ 'Cat', 'Dog', 'Fish' ]
# Just one -, When you don't write array values , The default value is null
# It can be said that yaml No, undefined, So it defaults to null Fill in
- # => [ null ]
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Pure quantity
Pure quantity ( Literal ) Is the most basic , Nonseparable value
boolean:
- true # true,True, TRUE All can
- false # false,False, FALSE All can
string:
# Special characters can be wrapped in double quotes or single quotes --- No quotation marks are recommended
- Klaus # => klaus, 'klaus', "Klaus" All can
# If there are special symbols , You need to wrap it in quotation marks
- 'name: Klaus' # => 'name: Klaus'
- Klaus Wang # => 'Klaus Wang'
# Strings can be split into multiple lines , Each line is converted to a space
- Klaus
Wang # => 'Klaus Wang'
number:
# and js in number equally , It can be an integer , It can also be a floating-point number
- 10 # => 10, 0.1, 12.5 All can
# Binary support , octal , Hexadecimal ( The hexadecimal ID must be all lowercase That is, it needs to be written as 0o, 0x, 0b ...)
- 0b11000 # => 0o30, 0x18 All can
- 0B11000 # => '0B11000' If the hexadecimal identifier is written in uppercase , Then it will be recognized as a string
# Letters in hexadecimal other than hexadecimal identifiers are not case sensitive
- 0x1A # 0x1a and 0x1A The conversion result is the same
- 6.8523015e+5 # You can use scientific counting
# yaml There is no undefined This data type
# Use ~ It means null
# null、Null、NULL and ~ It's all empty , If you don't specify a value, it's empty by default
null: ~
# When an object does not write a value , The default value is null
name: # => { name: null }
# Date must use ISO 8601 Format , namely yyyy-MM-dd
date:
- 2018-02-17
# Time use ISO 8601 Format , Use... Between time and date T Connect , Finally using + Represents the time zone
datetime:
- 2018-02-17T15:02:31+08:00
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YAML Two exclamation marks are allowed ( Double sense exclamation mark + The target type ), Cast data types
e: !!str 123
f: !!str true
# => { e: '123', f: 'true' }
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Anchor point
defaults: &defaults # Set anchor
adapter: postgres
host: localhost
adapter: *defaults # Use anchors
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human: &base # Add name is base The anchor point
body: 1
hair: 999
singer:
<<: *base # quote base Anchor point , When instantiated, it expands automatically
skill: sing # Add additional properties
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- &showell Steven
- Clark
- Brian
- Oren
- *showell
# => [ 'Steven', 'Clark', 'Brian', 'Oren', 'Steven' ]
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js-yaml
js-yaml It's a problem that can be resolved yml file , And convert it to JavaScript The library of objects
install
npm install js-yaml
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Use
const yaml = require('js-yaml');
const fs = require('fs');
const doc = yaml.load(fs.readFileSync('./foo.yml', 'utf8'));
console.log(doc);
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