map.md

map

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

Apply projection with each value from source.

Examples

Example 1: Add 10 to each number

( jsBin | jsFiddle )

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

Example 2: Map to single property

( jsBin | jsFiddle )

//emit ({name: 'Joe', age: 30}, {name: 'Frank', age: 20},{name: 'Ryan', age: 50})
const source = Rx.Observable.from([
  { name: 'Joe', age: 30 },
  { name: 'Frank', age: 20 },
  { name: 'Ryan', age: 50 }
]);
//grab each persons name
const example = source.map(person => person.name);
//output: "Joe","Frank","Ryan"
const subscribe = example.subscribe(val => console.log(val));

Related Recipes

• Smart Counter

Additional Resources

• map 📰 - Official docs
• map vs flatMap 📹 - Ben Lesh
• Transformation operator: map and mapTo 📹 💵 - André Staltz

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