Looping through object and setting as values in second object javascript

Question

I have an array, which need to be the keys in my object. I also have an object with the same keys and a default property, which I need to set as the value to my keys in the object I need to build. I'm stuck at how to loop and set the key/values in the empty object. Thanks!!

myFinalObj starts off as an empty object.

My starting object

var startingObj = {
  'one' : {'default': 1, 'name': 'un'},
  'two' : {'default': 2, 'name': 'deux'},
  'three': {'default': 3, 'name': 'trois'}
}

My Array

var myArray = ['one', 'two', 'three'];

My finished Object

var myFinalObj = {
  'one' : 1,
  'two' : 2,
  'three' : 3
}

if each position of the startingObj, you have the key, why you need myArray? — Pablo
– Pablo, Commented Nov 20, 2015 at 19:03
Maybe I don't? But then how would I loop the data to get the object desired? — tester123
– tester123, Commented Nov 20, 2015 at 19:04
What have you tried? We're not here to do your (home)work for you, but to answer specific questions about problems you're having. Try some things yourself, you might come up with the answer on your own, and if not, identify specific questions you can ask. — blm
– blm, Commented Nov 20, 2015 at 19:06
you would get 10 different answer here you haven't showed us what you've tried to get the result — CY5
– CY5, Commented Nov 20, 2015 at 19:07

lorefnon · Accepted Answer · 2015-11-20 19:16:28Z

2

var myFinalObj = myArray.reduce((memo, name) => { 
  memo[name] = startingObj[name].default 
  return memo 
}, {})

Quoting from MDN :

The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.

Arrow functions are a recent addition to javascript, and if your environment does not support them you can use the more verbose but equivalent :

 var myFinalObj = myArray.reduce(function(memo, name) { 
  memo[name] = startingObj[name].default 
  return memo 
}, {})

For IE < 9 the reduce function is also not available but you can use the polyfill available in the same MDN article .

edited Nov 20, 2015 at 19:16

answered Nov 20, 2015 at 19:10

lorefnon

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2 Comments

Sterling Archer Over a year ago

Could you explain this answer please?

lorefnon Over a year ago

I have added an explanation. Please review and let me know if any more clarifications are required.

Patrick Steadman · Accepted Answer · 2015-11-20 19:06:44Z

0

var startingObj = {
  'one': {
    'default': 1,
    'name': 'un'
  },
  'two': {
    'default': 2,
    'name': 'deux'
  },
  'three': {
    'default': 3,
    'name': 'trois'
  }
}


var myArray = ['one', 'two', 'three'];

var finalObject = {};

myArray.forEach(function(value){
 finalObject[value] = startingObject[value]['default']; 
}

answered Nov 20, 2015 at 19:06

Patrick Steadman

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Comments

Matthew · Accepted Answer · 2015-11-20 19:06:56Z

0

You can set property keys using obj["key"]=value syntax, so this should work:

var myFinalObject={};
for(var i=0;i<myArray.length;i++){
    myFinalObj[myArray[i]]=startingObj[myArray[i]];
}

answered Nov 20, 2015 at 19:06

Matthew

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Comments

Downhillski · Accepted Answer · 2015-11-20 19:07:18Z

0

Recommend using for(.. in ..) or for (var i=0;i<..;i++) as Array.forEach might not be supported in older browsers.

var myArray = ['one', 'two', 'three'];
var startingObj = {
  'one' : {'default': 1, 'name': 'un'},
  'two' : {'default': 2, 'name': 'deux'},
  'three': {'default': 3, 'name': 'trois'}
}
var myFinalObj = {};
for (key in myArray) {
	myFinalObj[myArray[key]] = startingObj[myArray[key]].default;
}
console.log(myFinalObj);

answered Nov 20, 2015 at 19:07

Downhillski

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Comments

jordan · Accepted Answer · 2015-11-20 19:08:18Z

0

Try this:

var startingObj = {
  'one' : {'default': 1, 'name': 'un'},
  'two' : {'default': 2, 'name': 'deux'},
  'three': {'default': 3, 'name': 'trois'}
}

var myArray = ['one', 'two', 'three'];

var myFinalObj = {}

for(n in myArray){
    if(startingObj.hasOwnProperty(myArray[n])){
        myFinalObj[myArray[n]] = startingObj[myArray[n]].default
    }
}

answered Nov 20, 2015 at 19:08

jordan

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Comments

Scott Schwalbe · Accepted Answer · 2015-11-20 19:08:24Z

0

function buildObj(startObj, keyArr, finalObj) {
  var currKey;
  for (var i = 0; i < keyArr.length; i++) {
    currKey = keyArr[i];
    finalObj[currKey] = startObj[currKey]['default'];
  }
}

var myFinalObj = {};
buildObj(startingObj, myArray, myFinalObj);

answered Nov 20, 2015 at 19:08

Scott Schwalbe

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Comments

leo.fcx · Accepted Answer · 2015-11-20 19:09:12Z

0

Use this simple code:

var myFinalObj = {};
myArray.forEach(function(key){
    myFinalObj[key] = startingObj[key].default;
});
console.log(myFinalObj)

answered Nov 20, 2015 at 19:09

leo.fcx

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Comments

user2263572 · Accepted Answer · 2015-11-20 19:13:15Z

0

Is this what you're trying to do? Based on your test case listed above it seems to work.

  var startingObj = {
  'one' : {'default': 1, 'name': 'un'},
  'two' : {'default': 2, 'name': 'deux'},
  'three': {'default': 3, 'name': 'trois'}
}

var myArray = ['one', 'two', 'three'];

var return_Obj = {}

for (var i = 0; i < myArray.length; i++){
    for (var key in startingObj){
        if (key == myArray[i]){
           var val = startingObj[key]['default']
        break
        }

    }
    return_Obj[myArray[i]] = val
}

console.log(return_Obj)

answered Nov 20, 2015 at 19:13

user2263572

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