You can use Array#find.

let arr = [
  {
    "enabled": true,
    "deviceID": "eI2K-6iUvVw:APA",
  },
  {
    "enabled": true,
    "deviceID": "e_Fhn7sWzXE:APA",
  },
  {
    "enabled": true,
    "deviceID": "e65K-6RRvVw:APA",
  },
];

const id = 'eI2K-6iUvVw:APA';

arr.find(v => v.deviceID === id).enabled = false;

console.log(arr);

It could do the trick !

var item = {};
var results={};

item.id = '50'
item.area = 'Mexico'
item.gender = null
item.birthdate = null

results.id = '50'
results.area = null
results.gender = 'Male'
results.birthdate = null

Object.keys(item).forEach(function(key) {
  if (item[key] == null || item[key] == 0) {
    item[key] = results[key];
  }
})
document.getElementById('dbg').innerHTML ='<pre>' + JSON.stringify(item , null , ' ') + '</pre>';

console.dir(item);

<div id='dbg'></div>

You can use findIndex to find the index in the array of the object and replace it as required:

var item = {...}
var items = [{id:2}, {id:2}, {id:2}];

var foundIndex = items.findIndex(x => x.id == item.id);
items[foundIndex] = item;

This assumes unique IDs. If your IDs are duplicated (as in your example), it's probably better if you use forEach:

items.forEach((element, index) => {
    if(element.id === item.id) {
        items[index] = item;
    }
});

for(var i=0; i<result.length; i++)
    if(result[i].length >= 2)
        result[i][1] = result[i][1].replace(/^Total$/, "xxxx").replace(/^Data$/, "DDDD");

The javascript object should be iterated and then each value of name can be checked and replaced. There are checks such as hasOwnProperty() that can be used to make sure you are not iterating objects that are missing "items" or "name" for better error handling.

var data = {
  "responses": {
    "firstKey": {
      "items": {
        "name": "test name one"
      }
    },
    "anotherKey": {
      "items": {
        "name": "test name two"
      }
    },
    "oneMoreKey": {
      "items": {
        "name": "John"
      }
    }
  }
};

Given the JSON above you can use a simple for statement to iterate and then check each name for some value and replace.

for(var key in data.responses){
    if ((data.responses[key].items.name).match(/test name/)){
       data.responses[key].items.name = "N/A";
    } 
}

To check your replacements you can log data to the console.

console.log(JSON.stringify(data));

let newlist = list.map(e => ({...e, name: e.nationality}) )

• e is for "element", where the .map method touches each element in a source array, and then returns a new array.

• newlist will have your modified array. list remains unchanged.

• e => begins an "arrow function". I want to return an object, but objects require curly braces, just like a function body. Defining an object {} and wrapping it in () sentinels tells JS that "these curlies are not a function body"

• without a function body, the "arrow function" expects a statement which it will then return by default without specifically using return keyword.

• ...e does a js "spread" on the e variable. It takes the entire contents of e and puts them right there as part of the new object. It then replaces the contents of the name property with data from the current element.

The long way:

let newlist = list.map(function (element) {
	element.name = element.nationality
	return element
})

Next to the way you proposed yourself, here is a classic loop approach. As mentioned by someone in a comment, it's more stable because you don't risk screwing the object up and throwing an error when trying to parse it back. On the other hand, some questions arise (see bottom).

Be careful, though, as the needle will be used as a regular expression. You may want to consider adding some sort of quoting to it.

I hope I didn't overlook anything, so test it and play around with it. Here you can find a fiddle.

/**
  * Replaces all occurrences of needle (interpreted as a regular expression with replacement and returns the new object.
  * 
  * @param entity The object on which the replacements should be applied to
  * @param needle The search phrase (as a regular expression)
  * @param replacement Replacement value
  * @param affectsKeys[optional=true] Whether keys should be replaced
  * @param affectsValues[optional=true] Whether values should be replaced
  */
Object.replaceAll = function (entity, needle, replacement, affectsKeys, affectsValues) {
    affectsKeys = typeof affectsKeys === "undefined" ? true : affectsKeys;
    affectsValues = typeof affectsValues === "undefined" ? true : affectsValues;

    var newEntity = {},
        regExp = new RegExp( needle, 'g' );
    for( var property in entity ) {
        if( !entity.hasOwnProperty( property ) ) {
            continue;
        }

        var value = entity[property],
            newProperty = property;

        if( affectsKeys ) {
            newProperty = property.replace( regExp, replacement );
        }

        if( affectsValues ) {
            if( typeof value === "object" ) {
                value = Object.replaceAll( value, needle, replacement, affectsKeys, affectsValues );
            } else if( typeof value === "string" ) {
                value = value.replace( regExp, replacement );
            }
        }

        newEntity[newProperty] = value;
    }

    return newEntity;
};

The last two parameters are optional, so it's perfectly fine to just call it like this:

var replaced = Object.replaceAll( { fooman: "The dog is fooking" }, "foo", "bar" );

However, there are still edge cases where it's unclear what should happen. For example:

// do you expect it to stay undefined or change type and become "undebazed"?
console.log( Object.replaceAll( { x: undefined }, "fin", "baz" ) );

// null or "nalala"?
console.log( Object.replaceAll( { x: null }, "ull", "alala" ) );

Or

// true or false?
console.log( Object.replaceAll( { x: true }, "true", "false" ) );

// true or "foo"?
console.log( Object.replaceAll( { x: true }, "true", "foo" ) );

And the same for numbers

// 1337 or 1007?
console.log( Object.replaceAll( { x: 1337 }, "33", "00" ) );

// 1337 or "1foo7"
console.log( Object.replaceAll( { x: 1337 }, "33", "foo" ) );

None of these cases are currently handled in my method – only objects (for nesting) and strings will be touched.

Use Array.map and Array.find():

const allItems = [
  { 'id': 1, 'category_id': 1, 'text': 'old' },
  { 'id': 2, 'category_id': 1, 'text': 'old' }
];

const newItems = [
  { 'id': 1, 'category_id': 1, 'text': 'new', 'more_info': 'abcd' },
  { 'id': 2, 'category_id': 1, 'text': 'new', 'more_info': 'abcd' }
];

const result = allItems.map(x => {
  const item = newItems.find(({ id }) => id === x.id);
  return item ? item : x;
});

console.log(result);

This can even be shortened by using a logical or to return the original item when the call to find returns undefined:

const result = allItems.map(x => newItems.find(({ id }) => id === x.id) || x);

Regarding your code, you can't use indexOf since it only compares primitive values or references in the case of arrays and objects.

Assuming your JSON array is stored in the variable data:

data.forEach(item => item.label = item.name)

This would be sufficient to duplicate the name property as the label property for each item in the array.