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Table Constructors

Syntaxes

There are 3 different syntaxes to construct tables.

  • Standard Syntax: { key = value, ... }
  • Expression Syntax: { [expression] = value, ... }
  • JSON Syntax: { "key": value, ... }

You are free to mix and match the different syntaxes in the same table constructor: 

local a = { cat = "dog", "abc": "def", [1+4] = "some number" }
# Creates: { "cat": "dog", "abc": "def", 5: "some number" }

Standard Syntax

  • Key must be a string literal without quotes. String cannot start with a number.
  • Format: { key = value, ... }
# Example:
local myTable = { myKey = 6 }   # Creates: { "myKey": 6 }
                                # Note: It does not matter if `myKey` is
                                # also the name of a variable, the
                                # key will still be string literal "myKey"

Expression Syntax

  • The key is the evaluated expression inside []
  • Format: { [expr] = value, ... }
# Example 1:
local myTable = { [7] = 6 }          # Creates: { 7: 6 }

# Example 2:
local myKey = "dog"
local myTable = { [myKey] = 6 }      # Creates: { "dog": 6 }

JSON Syntax

  • The key must be a string literal. Cannot use a variable or number for the key.
  • Format: { "key": value, ... }
# Example:
local myTable = { "myKey": 6 }      # Creates: { "myKey": 6 }

More Examples

local a = { [3] = "abc" }           # Creates: { 3: "abc" }

# local b = { 3 = "abc" }           # invalid syntax, in Standard Syntax,
                                    # key must not started with a number

# local c = { 3: "abc" }            # invalid syntax, in JSON Syntax,
                                    # key must be a "string"

local d = { "3": "abc" }            # Creates: { "3": "abc" }

# local e = { "3" = "abc" }         # invalid syntax, in Standard Syntax,
                                    # string key must not have quotes

local myKey = "dog"

local f = { myKey = "test" }        # { "myKey": "test" }

local g = { [myKey] = "test" }      # { "dog": "test" }

# local h = { myKey: 4 }            # invalid syntax, in JSON Syntax,
                                    # key must be a "string"

local i = { "myKey": "test" }       # { "myKey": "test" }