map.md

map

signature: map(project: Function, thisArg: any): Observable

Apply projection with each value from source.

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New to transformation operators? Check out the article Get started transforming streams with map, pluck, and mapTo!

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Examples

Example 1: Add 10 to each number

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { from } from 'rxjs';
import { map } from 'rxjs/operators';

//emit (1,2,3,4,5)
const source = from([1, 2, 3, 4, 5]);
//add 10 to each value
const example = source.pipe(map(val => val + 10));
//output: 11,12,13,14,15
const subscribe = example.subscribe(val => console.log(val));

Example 2: Map to single property

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { from } from 'rxjs';
import { map } from 'rxjs/operators';

//emit ({name: 'Joe', age: 30}, {name: 'Frank', age: 20},{name: 'Ryan', age: 50})
const source = from([
  { name: 'Joe', age: 30 },
  { name: 'Frank', age: 20 },
  { name: 'Ryan', age: 50 }
]);
//grab each persons name, could also use pluck for this scenario
const example = source.pipe(map(({ name }) => name));
//output: "Joe","Frank","Ryan"
const subscribe = example.subscribe(val => console.log(val));

Related Recipes

• Alphabet Invasion Game
• Battleship Game
• Catch The Dot Game
• Game Loop
• HTTP Polling
• Lockscreen
• Memory Game
• Mine Sweeper Game
• Save Indicator
• Smart Counter
• Space Invaders Game
• Stop Watch
• Swipe To Refresh
• Tetris Game
• Type Ahead

Additional Resources

• map 📰 - Official docs
• map - In Depth Dev Reference
• map vs flatMap 🎥 - Ben Lesh
• Transformation operator: map and mapTo 🎥 💵 - André Staltz

• Build your own map operator 🎥 - Kwinten Pisman

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📁 Source Code: https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/map.ts