Contrasting type[] (array) with [type] (tuple)

Question

Contrasting type[] (array) with [type] (tuple)

If we imagine having two interfaces:

interface WithStringArray1 {
    property: [string]
}

interface WithStringArray2 {
    property: string[]
}

Let's define variables of these types:

let type1:WithStringArray1 = {
   property: []
}

let type2:WithStringArray2 = {
    property: []
}

The first initialization results in an error message:

TS2322: Type '{ property: undefined[]; }' is not assignable to type 'WithStringArray1'.
Types of property 'property' are incompatible.
Type 'undefined[]' is not assignable to type '[string]'.
Property '0' is missing in type 'undefined[]'.

However, the second one is successful.

What sets apart [string] from string[]?

typescript

Answer 1

Answer №1

[text] signifies a tuple containing only one text element. Tuples are sequences of items that are ordered, generally of a fixed size.
text[] represents an array of texts. Arrays can have a variable length, including being empty.

To use the Tuple properly in your scenario, you would do:

let type2:WithStringArray2 = {
    property: ['aString']
};

Refer to the Official Documentation

Answer 2

[text] signifies a tuple containing only one text element. Tuples are sequences of items that are ordered, generally of a fixed size.
text[] represents an array of texts. Arrays can have a variable length, including being empty.

To use the Tuple properly in your scenario, you would do:

let type2:WithStringArray2 = {
    property: ['aString']
};

Refer to the Official Documentation

Answer 3

Answer №2

When examining a tuple with three variables, the distinction becomes evident.

let t: [number, string?, boolean?];
t = [42, "hello", true];

let tuple : [string] represents a tuple of strings, while let arr : string[] denotes an array of strings.

Answer 4

When examining a tuple with three variables, the distinction becomes evident.

let t: [number, string?, boolean?];
t = [42, "hello", true];

let tuple : [string] represents a tuple of strings, while let arr : string[] denotes an array of strings.

Contrasting type[] (array) with [type] (tuple)

Answer №1

Answer №2

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