The YAML equivalent of an Array of Objects in JSON

# The YAML equivalent of an Array of Objects in JSON

The YAML equivalent of an array of objects in JSON is a sequence of objects.

Each object in the sequence has to start with a hyphen -.

Assume you have the following array of objects in JSON.

employees.json

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[
  {
    "id": 1,
    "name": "Alice",
    "languages": ["Java", "JavaScript"]
  },
  {
    "id": 2,
    "name": "Bobby",
    "languages": ["Python", "JavaScript"]
  },
  {
    "id": 3,
    "name": "Carl",
    "languages": ["Typescript", "JavaScript"]
  }
]

It translates to the following YAML sequence.

employees.yaml

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- id: 1
  name: Alice
  languages:
    - Java
    - JavaScript
- id: 2
  name: Bobby
  languages:
    - Python
    - JavaScript
- id: 3
  name: Carl
  languages:
    - Typescript
    - JavaScript

yaml json array of objects

Make sure the keys in the objects are indented consistently.

For example, the following YAML code is syntactically correct.

employees.yaml

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# ✅ Code indented correctly
- id: 1
  name: Alice
  languages:
    - Java
    - JavaScript

Whereas the following code causes a syntax error.

employees.yaml

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# ⛔️ Error: YAMLException: bad indentation of a mapping entry at line 2, column 10:
- id: 1
    name: Alice
  languages:
    - Java
    - JavaScript

Notice that the name key is not indented consistently with the other keys.

Notice that the first property (id) of each object is prefixed with a hyphen - to mark each object as an element in an array (YAML sequence).

Let's look at an example of an array of objects that has nested object values.

employees.json

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[
  {
    "id": 1,
    "name": "Alice",
    "languages": [
      "Java",
      "JavaScript"
    ],
    "address": {
      "country": "Austria",
      "city": "Vienna"
    }
  },
  {
    "id": 2,
    "name": "Bobby",
    "languages": [
      "Python",
      "JavaScript"
    ],
    "country": "Belgium",
    "city": "Ghent"
  },
  {
    "id": 3,
    "name": "Carl",
    "languages": [
      "Typescript",
      "JavaScript"
    ],
    "address": {
      "country": "Canada",
      "city": "Ottawa"
    }
  }
]

The JSON above translates to the following YAML.

employees.yaml

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- id: 1
  name: Alice
  languages:
    - Java
    - JavaScript
  address:
    country: Austria
    city: Vienna
- id: 2
  name: Bobby
  languages:
    - Python
    - JavaScript
  country: Belgium
  city: Ghent
- id: 3
  name: Carl
  languages:
    - Typescript
    - JavaScript
  address:
    country: Canada
    city: Ottawa

If you need to represent an array in YAML, you would use the following syntax.

employee.yaml

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- Alice
- Bobby
- Carl

Notice that each element is prefixed with a hyphen and the elements are indented consistently.

The YAML sequence above translates to the following JSON array.

employee.json

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[
  "Alice",
  "Bobby",
  "Carl"
]

If you need to represent a simple object, you would separate each key and value with a colon.

For example, the following YAML.

employees.yaml

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id: 1
name: Alice
salary: 500
is_programmer: true

Translates to the following JSON object.

employee.json

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{
  "id": 1,
  "name": "Alice",
  "salary": 500,
  "is_programmer": true
}

If your object contains a property that has an array value, each array element must start with a hyphen.

employees.yaml

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id: 1
name: Alice
salary: 500
is_programmer: true
languages:
  - Java
  - JavaScript
  - Python

The YAML above translates to the following JSON object.

employee.json

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{
  "id": 1,
  "name": "Alice",
  "salary": 500,
  "is_programmer": true,
  "languages": [
    "Java",
    "JavaScript",
    "Python"
  ]
}

If your object has a nested object property, you would define it as follows.

employees.yaml

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id: 1
name: Alice
salary: 500
is_programmer: true
languages:
  - Java
  - JavaScript
  - Python
address:
  country: Austria
  city: Vienna

The YAML above translates to the following JSON.

employees.json

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{
  "id": 1,
  "name": "Alice",
  "salary": 500,
  "is_programmer": true,
  "languages": [
    "Java",
    "JavaScript",
    "Python"
  ],
  "address": {
    "country": "Austria",
    "city": "Vienna"
  }
}

If you need to specify an array property of the object, you would prefix each element with a hyphen.

employees.yaml

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id: 1
name: Alice
salary: 500
is_programmer: true
languages:
  - Java
  - JavaScript
  - Python
address:
  country: Austria
  city: Vienna
  post_codes:
    - 123
    - 456
    - 789

The YAML above translates to the following JSON.

employees.json

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{
  "id": 1,
  "name": "Alice",
  "salary": 500,
  "is_programmer": true,
  "languages": [
    "Java",
    "JavaScript",
    "Python"
  ],
  "address": {
    "country": "Austria",
    "city": "Vienna",
    "post_codes": [
      123,
      456,
      789
    ]
  }
}

If you need to define an object that has a key with a value that is an array of objects, use the following syntax.

employees.yaml

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Accounting:
  - id: 1
    name: Alice
    start_date: 2023-01-01
  - id: 2
    name: Bobby
    start_date: 2023-01-05
  - id: 3
    name: Carl
    start_date: 2023-01-03

The YAML above translates to the following JSON.

employees.json

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{
  "Accounting": [
    {
      "id": 1,
      "name": "Alice",
      "start_date": "2023-01-01T00:00:00.000Z"
    },
    {
      "id": 2,
      "name": "Bobby",
      "start_date": "2023-01-05T00:00:00.000Z"
    },
    {
      "id": 3,
      "name": "Carl",
      "start_date": "2023-01-03T00:00:00.000Z"
    }
  ]
}

You might also see hyphens being placed on separate lines.

emplyoees.yaml

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Accounting:
  -
    id: 1
    name: Alice
    start_date: 2023-01-01
  -
    id: 2
    name: Bobby
    start_date: 2023-01-05
  -
    id: 3
    name: Carl
    start_date: 2023-01-03

The YAML above is also perfectly valid syntax and translates to the same JSON.

employees.json

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{
  "Accounting": [
    {
      "id": 1,
      "name": "Alice",
      "start_date": "2023-01-01T00:00:00.000Z"
    },
    {
      "id": 2,
      "name": "Bobby",
      "start_date": "2023-01-05T00:00:00.000Z"
    },
    {
      "id": 3,
      "name": "Carl",
      "start_date": "2023-01-03T00:00:00.000Z"
    }
  ]
}

If some of your nested objects have keys that have object values, you would use the following syntax.

employees.yaml

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Accounting:
  - id: 1
    name: Alice
    start_date: 2023-01-01
    address:
      country: Austria
      city: Vienna
  - id: 2
    name: Bobby
    start_date: 2023-01-05
    address:
      country: Belgium
      city: Brussels
  - id: 3
    name: Carl
    start_date: 2023-01-03
    address:
      country: Canada
      city: Ottawa

The YAML above translates to the following JSON.

employees.json

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{
  "Accounting": [
    {
      "id": 1,
      "name": "Alice",
      "start_date": "2023-01-01T00:00:00.000Z",
      "address": {
        "country": "Austria",
        "city": "Vienna"
      }
    },
    {
      "id": 2,
      "name": "Bobby",
      "start_date": "2023-01-05T00:00:00.000Z",
      "address": {
        "country": "Belgium",
        "city": "Brussels"
      }
    },
    {
      "id": 3,
      "name": "Carl",
      "start_date": "2023-01-03T00:00:00.000Z",
      "address": {
        "country": "Canada",
        "city": "Ottawa"
      }
    }
  ]
}

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The YAML equivalent of an Array of Objects in JSON

# The YAML equivalent of an Array of Objects in JSON

Borislav Hadzhiev