reduce operator basics

mediumrxjs_episode1_example1_reduce.ts

// Example 1: Simple Reduce
console.log('Reduce');
//The Observable consumes an array of numbers and spews each number out individually to the reduce operator.
Observable.from([1, 2, 3, 4, 5])
    //reduce accepts two parameters (accumulator,current,index) and an optional seed, which is just an initial value 
    //set to 0 in this case.
    //the lambda function adds the current value to the accumulator and repeats for all numbers in the array
    .reduce((accumulator, value, index) => (accumulator + value), 0) 
    .subscribe(response => {
      console.log(response); //logs the response
    });

//Output
//Reduce
//15