How to update array value javascript?

Question

I have an array of 3 objects of keyValue constructor in javacsript:

  function keyValue(key, value){
    this.Key = key;
    this.Value = value;
  };

  var array = [];
  array.push(new keyValue("a","1"),new keyValue("b","2"),new keyValue("c","3"));

I also have a function 'Update' which takes keyValue object as parameter and updates the value of that object in the array:

  function Update(keyValue, newKey, newValue)
  {
    //Now my question comes here, i got keyValue object here which i have to 
    //update in the array i know 1 way to do this 

    var index = array.indexOf(keyValue);
    array[index].Key = newKey;
    array[index].Value = newValue; 
  }

But I want a better way to do this if there is one.

Why not use an object? var dict = { "a": 1, "b": 2, "c": 3 }; and then you can update it like dict.a = 23; or dict["a"] = 23;... — canon
– canon, Commented Oct 25, 2012 at 13:28

I Hate Lazy · Accepted Answer · 2012-10-25 13:28:28Z

23

"But i want to know a better way to do this, if there is one ?"

Yes, since you seem to already have the original object, there's no reason to fetch it again from the Array.

  function Update(keyValue, newKey, newValue)
  {
    keyValue.Key = newKey;
    keyValue.Value = newValue; 
  }

answered Oct 25, 2012 at 13:28

I Hate Lazy

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Comments

Community · Accepted Answer · 2017-05-23 12:18:07Z

18

Why not use an object¹?

var dict = { "a": 1, "b": 2, "c": 3 };

Then you can update it like so

dict.a = 23;

or

dict["a"] = 23;

If you wan't to delete² a particular key, it's as simple as:

delete dict.a;

_{¹ See Objects vs arrays in Javascript for key/value pairs.
² See the delete operator.}

edited May 23, 2017 at 12:18

CommunityBot

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answered Oct 25, 2012 at 13:31

canon

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2 Comments

I Hate Lazy Over a year ago

You're not updating the key. Just the value. Though the actual situation may not allow this. The current storage would seem to imply that the key will not be known except by some alternate reference to this object.

I Hate Lazy Over a year ago

Sure, point is that in the question there's an alternate reference to an object with two properties. We don't know the reason, but it very well may not be suitable to have the Key property as the lookup identifier.

Martin54 · Accepted Answer · 2019-01-24 18:51:45Z

8

function Update(key, value)
{    
    for (var i = 0; i < array.length; i++) {
        if (array[i].Key == key) {
            array[i].Value = value; 
            break;
        }
    }
}

edited Jan 24, 2019 at 18:51

Martin54

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answered Oct 25, 2012 at 13:32

Jerry

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Comments

Alex K. · Accepted Answer · 2012-10-25 13:35:02Z

4

How about;

function keyValue(key, value){
    this.Key = key;
    this.Value = value;
};
keyValue.prototype.updateTo = function(newKey, newValue) {
    this.Key = newKey;
    this.Value = newValue;  
};

array[1].updateTo("xxx", "999");

answered Oct 25, 2012 at 13:35

Alex K.

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Comments

noquierouser · Accepted Answer · 2020-04-09 01:14:16Z

3

If you want to reassign an element in an array, you can do the following:

var blah = ['Jan', 'Fed', 'Apr'];

console.log(blah);

function reassign(array, index, newValue) {
    array[index] = newValue;
    return array;
}

reassign(blah, [2], 'Mar');

edited Apr 9, 2020 at 1:14

noquierouser

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answered Apr 8, 2020 at 18:19

john doe

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1 Comment

john doe Over a year ago

P.s. you can also use this same function assignment for objects. after creating objects, the function assignment would go like this, function (obj, key, value).

Deathstalker · Accepted Answer · 2020-11-10 22:57:31Z

So I had a problem I needed solved. I had an array object with values. One of those values I needed to update if the value == X.I needed X value to be updated to the Y value. Looking over examples here none of them worked for what I needed or wanted. I finally figured out a simple solution to the problem and was actually surprised it worked. Now normally I like to put the full code solution into these answers but due to its complexity I wont do that here. If anyone finds they cant make this solution work or need more code let me know and I will attempt to update this at some later date to help. For the most part if the array object has named values this solution should work.

            $scope.model.ticketsArr.forEach(function (Ticket) {
                if (Ticket.AppointmentType == 'CRASH_TECH_SUPPORT') {
                    Ticket.AppointmentType = '360_SUPPORT'
                }
            });

Full example below _____________________________________________________

   var Students = [
        { ID: 1, FName: "Ajay", LName: "Test1", Age: 20 },
        { ID: 2, FName: "Jack", LName: "Test2", Age: 21 },
        { ID: 3, FName: "John", LName: "Test3", age: 22 },
        { ID: 4, FName: "Steve", LName: "Test4", Age: 22 }
    ]

    Students.forEach(function (Student) {
        if (Student.LName == 'Test1') {
            Student.LName = 'Smith'
        }
        if (Student.LName == 'Test2') {
            Student.LName = 'Black'
        }
    });

    Students.forEach(function (Student) {
        document.write(Student.FName + " " + Student.LName + "<BR>");
    });

I decided to circle back to this and give a full example with code anyone can use. I tested it in multiple browsers without any extra libs added, and it worked perfectly.

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