Creating a new javascript object based on another object

Question

I'm trying to create a new javascript object that'll have new key names based on another object. I'm almost there, but my code fails at the line // fails here with Uncaught TypeError: Cannot set property 'name' of undefined . Any idea how to get this right? Also, is there a more efficient way to build a new object in this case? I need it work on older IE browsers, hence this approach.

    originalObj = {"name":"John","age":30,"state":"CA","country":"USA"};
    
    objCodes = {"name":101,"age":102,"state":103,"country":104};
    
    // newObj = {101:"John", 102:30,103:"CA",104:"USA"};
        
    newObj = {};
    
    for (var i in originalObj) {
      if (objCodes.hasOwnProperty(i)) {
          // console.log(i, originalObj[i]);
          console.log(objCodes[i],originalObj[i])
          newObj.objCodes[i] = originalObj[i] // fails here
          
        
       }
    }
    
    console.log(newObj);

newObj[objCodes[i]] = originalObj[i]

Guy Incognito
– Guy Incognito

2020-06-25 07:32:52 +00:00
Commented Jun 25, 2020 at 7:32 — Guy Incognito
– Guy Incognito, Commented Jun 25, 2020 at 7:32

RacoonOnMoon · Accepted Answer · 2020-06-25 07:34:47Z

1

Just change the line like in the snippet below

originalObj = {"name":"John","age":30,"state":"CA","country":"USA"};
    
    objCodes = {"name":101,"age":102,"state":103,"country":104};
    
    // newObj = {101:"John", 102:30,103:"CA",104:"USA"};
        
    newObj = {};
    
    for (var i in originalObj) {
      if (objCodes.hasOwnProperty(i)) {
          // console.log(i, originalObj[i]);
          console.log(objCodes[i],originalObj[i])
          newObj[objCodes[i]] = originalObj[i] // fails here
          
        
       }
    }
    
    console.log(newObj);

answered Jun 25, 2020 at 7:34

RacoonOnMoon

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Comments

Shreyash bhatt · Accepted Answer · 2020-06-25 08:15:32Z

1

originalObj = {"name":"John","age":30,"state":"CA","country":"USA"};

objCodes = {"name":101,"age":102,"state":103,"country":104};

// newObj = {101:"John", 102:30,103:"CA",104:"USA"};
    
newObj = {};

for (var i in originalObj) {
  if (objCodes.hasOwnProperty(i)) {
      // console.log(i, originalObj[i]);
      console.log(objCodes[i],originalObj[i])
      newObj[objCodes[i]] = originalObj[i] // fails here
      
    
   }
}

console.log(newObj);

Change the dotted notation to bracket notation. ~~Reason for this is JavaScript allows only valid names with dotted notation which cannot start with numeric value.And In your case the keys are set to be 101,102...and so on, which are invalid.~~

Edit : Dynamic property names can be used only through bracket notations, such as in your case where the property name is set using a variable.

edited Jun 25, 2020 at 8:15

answered Jun 25, 2020 at 7:44

Shreyash bhatt

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1 Comment

Guy Incognito Over a year ago

Because the newObj.objCodes[i] will not work regardless of what the value of objCodes[i] is, numerical values has nothing to do with it. You need newObj[objCodes[i]] because objCodes[i] is a variable and the newObj key is being set dynamically.

Lajos Arpad · Accepted Answer · 2020-06-25 08:20:39Z

0

You can get the keys, iterate them and copy the items like this:

originalObj = {"name":"John","age":30,"state":"CA","country":"USA"};

objCodes = {"name":101,"age":102,"state":103,"country":104};

// newObj = {101:"John", 102:30,103:"CA",104:"USA"};
    
newObj = {};

Object.keys(objCodes).forEach(i => newObj[objCodes[i]] = originalObj[i]);

answered Jun 25, 2020 at 8:20

Lajos Arpad

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