What does the `map` method mean in RxJS?

Question

I\'m learning RxJS by reading this tutorial http://reactive-extensions.github.io/learnrx/.

I have a hard time understanding the map method of Obse

Answer 1

Map in Rxjs used for projection, means you can transform the array in to entirely new array. In order to understand how Map works , we can implement our own map function using plain javascript.

Array.prototype.map = function(projectionFunction){
var results=[];
this.forEach(function(item) {
results.push(projectionFunction(item));
});
return results;
};

You can see I have written a map function which accepts an anonymous function as a parameter. This will be your function to apply the projection to transform the array. Inside the map function you can see iterating each item in a array , call the project function by passing each item and finally the result of the projection function will push to the results array.

JSON.stringify([1,2,3].map(function(x){return x+1;}))

Output

[2,3,4]