Let say I have a array like this:

[
  {
    name:"1",
    args: [1,2,3,4,5]
  },
  {
    name:"2",
    args: [2,3,4,5,6]
  }
]

What I want to do, is to remove all "args" that have a value < 4, to have the following result:

[
  {
    name:"1",
    args: [4,5]
  },
  {
    name:"2",
    args: [4,5,6]
  }
]

How can I do that using Observables (Rxjs). I tried with mergeMap, but it does seems to do what I want.

Let say I have a array like this:

[
  {
    name:"1",
    args: [1,2,3,4,5]
  },
  {
    name:"2",
    args: [2,3,4,5,6]
  }
]

What I want to do, is to remove all "args" that have a value < 4, to have the following result:

[
  {
    name:"1",
    args: [4,5]
  },
  {
    name:"2",
    args: [4,5,6]
  }
]

How can I do that using Observables (Rxjs). I tried with mergeMap, but it does seems to do what I want.

• javascript
• arrays
• rxjs
• observable

3 Answers 3

You can do this pretty easily using plain JS.

var data = [
  {
    name:"1",
    args: [1,2,3,4,5]
  },
  {
    name:"2",
    args: [2,3,4,5,6]
  }
];

var parsedData = data.map(function(el){
    el.args = el.args.filter(function(x){ return x >= 4; });
    return el;
});

console.log(parsedData);

If you want RxJS-way solution, it might look something like this:

ES6 syntax:

const arr = [
  {
    name:"1",
    args: [1,2,3,4,5]
  },
  {
    name:"2",
    args: [2,3,4,5,6]
  }
]

Rx.Observable
  .from(arr) // 1
  .map(item => { // 2
    return {
      ...item,
      args: item.args.filter(arg => arg >= 4) // 3
    }
  })
  .reduce((acc, value) => [...acc, value], []) // 4
  .subscribe(result => {
    console.log(result) // 5
  })

ES5 syntax:

var arr = [
  {
    name:"1",
    args: [1,2,3,4,5]
  },
  {
    name:"2",
    args: [2,3,4,5,6]
  }
]

Rx.Observable
  .from(arr)
  .map(function(item) {
    return {
        name: item.name,
        args: item.args.filter(function(arg) {
        return arg >= 4
      })
    }
  })
  .reduce(function(acc, value) {
    return [].concat(acc, value)
  }, [])
  .subscribe(function(result) {
    console.log(result)
  })

1. Create Observable sequence from array
2. Modify each streamed item in array corresponding to your needs
3. Actual args filtering
4. Reduce all streamed results into one array (you can remove this line if you want then process each item of array one-by-one, not the whole array)
5. Do something with result

Some useful links:

• Observable.from() method
• map() operator
• reduce() operator

observables are for manipulations of streams of data over time, so they are array like but they are not arrays. If this data is ing through an observable, you should just use map and then use normal array operators inside the observable map, because you're just manipulating a single data point in the stream:

source.map(data => data.map(d => Object.assign(d, {args:d.args.filter(v => v >= 4)})));