CODEWITHSUNDEEP
javascriptangular
Milad
Milad

Reputation: 28590

Javascript split object by key

Let's say I have bellow object : 

   var obj = {
         name:'Jone',
         age:'23',
         height:200,
         weight:400,
   }

I want this : 

   var obj1 = {
         name:'Jone',
         age:'23'
   }

   var obj2 = {
         height:200,
         weight:400
   }

Really what I'm looking for is obj.splice('age') meaning that split this object into two object , starting from age as the key.

I know I can loop and do it the hard way, but is there any equivalent easy nice way ?

Also, if there is any Angular2ish way(a hidden utility maybe ? ), would be even better.

EDIT : I don't exactly know what's inside the object , I just know my key is in there .

What I really am doing is I want to loop around an object , but I have an start point and i don't want to loop through all , I want to be able to cut that object and just start the loop from where I need.

    Object.keys(obj).map( function( value , index ) {
       // I'm just looping here to do some stuff , which is not related to the question here.


    } );

Obviously I'm looping over all the keys of this object , but I want to start from age .

I hope this is clear .

EDIT ; I know this is getting a little bit out of the board , but in Angular2 , we have a formModel and we can have multiple controlGroup inside it , I want to basically be able to find the first controlGroup that is invalid , that's it .

Upvotes: 2

Views: 9149

Answers (3)

Ankit Singh
Ankit Singh

Reputation: 24945

PLUNKER DEMO

From what I know and understood from your problem,

ControlGroup is an Object and as others have also noted that properties don't have a specific order, and you can't rely on it even if you know that it's in alphabetical order.

I assume that you either write the controlGroups using formBuilder or generate using a loop.

  • If you already have an array of what controlGroups are there going to be, just save them in an array like 

cgs = ['controlGroup1', 'controlGroup2', 'controlGroup3']

in the exact order that you will put them in the template. Now you know what you are looking for.

  • If you don't,
    • You can create an array
    • If you can't, just traverse the the DOM like

let domList = document.querySelectorAll('*[ngControlGroup]');
let cgEls = Array.apply(null, domList);
var cgs = [];  // will store the ordered list of controlGroups

cgEls.forEach((e) => {
 cgs.push(e.attributes.ngControlGroup.value);
})

NOW you know the order, check for thier validity one by one.

Hope it helps.

Upvotes: 1

Himmel
Himmel

Reputation: 3709

I know you're looking for a nice, simple solution, but it's really tough to create a new object without mapping over the keys to get the values. If you're open to using some ES6 syntax, the following solution might work for you.

var obj = {
     name:'Jone',
     age:'23',
     height:200,
     weight:400,
}

var newObj = Object.keys(obj)
  .slice(Object.keys(obj).indexOf('age'))
  .reduce((a, c) => Object.assign(a, { [c]: obj[c] }), {})

// newObj = { height: 200, weight: 400 }

With this method, you are at least only looping over the final two keys in the object.

Upvotes: 0

Polygon
Polygon

Reputation: 265

You could do this:

var obj = {
  name: 'Jone',
  age: '23',
  height: 200,
  weight: 400,
}

var obj1 = {}
var obj2 = {}

function splitAtAge(input) {
  var afterAge = 0;
  for (var i in input) {
    if (afterAge) {
      obj2[i] = input[i];
    } else {
      obj1[i] = input[i];
    }

    if (i == "age") {
      afterAge = true;
    }
  }
}


splitAtAge(obj);

It loops through the object and if a property is after "age", it adds it to obj2. Otherwise, it adds it to obj1.

It seems to work every time for me, but I would avoid doing this altogether if I were you because the properties of objects aren't really meant to have an order.

EDIT: I just realized that you are using Angular, with which I am not familiar. However, this pure JS code should still work.

Upvotes: 0

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