Add updating and destructuring examples. (#27628)
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@ -4,7 +4,7 @@ title: Tuple Type
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# Tuple Type
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Express an array in which a fixed number of elements of types is known, but not the same.
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Expresses an array with a fixed number of elements of known (but possibly different) types. For example:
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```typescript
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let arr: [string, number];
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@ -12,54 +12,75 @@ let arr: [string, number];
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// This is correct
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arr = ['Hello', 7];
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//This is incorrect
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// This is incorrect
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arr = [7, 'Hello'];
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```
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When accessing an element outside the known indices, it will use a union type:
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```typescript
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arr[3] = 'World!'
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arr[3] = 'World!';
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// OK, 'string' can be assigned to 'string | number'
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// Error, 'boolean' is not a 'string | number'
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arr[5] = false;
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// Error, 'boolean' is not a 'string | number'
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```
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## Properties
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In Typescript's type you can have some buit-in properties. Forexample length or some other unique each types.
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Tuples have some built-in properties, such as length.
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### length
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This property said, how many element has it's element.
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The number of elements:
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```typescript
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let tuple = []; //you can initialize it after the declaration too, not just the method above
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tuple[0] = 10;
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tuple[1] = 'Mike';
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let tuple = [10, 'Mike'];
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let number = tuple.length;
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//number = 2;
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// number = 2
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```
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## Built-in methods
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In Typescript's type you can use some built-in functions. Each type has common and unique methods.
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Below you can read about the most used ones of the tuple type's methods.
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Tuples have some built-in functions, such as adding a new element and removing an element:
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### pop()
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Removes the last element from a tuple.
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Removes the last element from a tuple and returns that element.
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```typescript
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var tuple = [10,'Emma',11,'Lily',12,'Mike Ross'];
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tuple.pop();
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//tuple = [10,'Emma',11,'Lily',12,]
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//We popped 'Mike Ross' from the tuple
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let tuple = [10,'Emma',11,'Lily',12,'Mike Ross'];
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let popped = tuple.pop();
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// tuple = [10,'Emma',11,'Lily', 12]
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// popped = 'Mike Ross'
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```
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### push()
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Adds element to the end of the tuple.
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Adds an element to the end of the tuple.
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```typescript
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var tuple = [10,'Emma',11,'Lily',12,'Mike Ross'];
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let tuple = [10,'Emma',11,'Lily',12,'Mike Ross'];
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tuple.push('Rachel Zane');
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//tuple = [10,'Emma',11,'Lily',12,'Mike Ross','Rachel Zane']
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// tuple = [10,'Emma',11,'Lily',12,'Mike Ross','Rachel Zane']
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```
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## Destructuring
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The following is an easy way to break apart a tuple in TypeScript:
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```typescript
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let tuple = ['sheep', 4];
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[a, b] = tuple;
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// a = 'sheep'
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// b = 4
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```
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## Updating
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You can initialize the tuple after the declaration:
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```typescript
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let tuple = [];
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tuple[0] = 'cow';
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tuple[1] = 'Mike';
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// tuple = ['cow', 'Mike']
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```
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You can update an existing tuple in the same way you update an array:
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```typescript
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let tuple = ['sheep', 4];
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tuple[0] = 'cow';
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// tuple = ['cow', 4]
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```
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[More info about tuples on TutorialsPoint](https://www.tutorialspoint.com/typescript/typescript_tuples.htm)
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