js object replacing values with input

Question

I want to store or save data in js object as follow:

var car= {};
car[number] = user_input;

giving...

car = {1:"Fiat"};

But I only want to have up to max three values.

car = {1:"Fiat", 2:"Honda"};// two values
car = {1:"Fiat", 2:"Honda", 3:"Ford"}; //three values

So, if there is another input after three values are already added, then I want it so that it will replace the first value like below:

car = {1:"Nissan", 2:"Honda", 3:"Ford"};

Then the second value will be replaced next and so on:

car = {1:"Nissan", 2:"Tesla", 3:"Ford"};

What would be an elegant way of designing this?

Any suggestions will be much appreciated.

EDIT:

To clarify the question, the key is id number such as "234" or "5432" or "2342".

For example:

car = {1233:"Nissan", 555:"Tesla", 3345:"Ford"};

yeah, it will have to be an object as there will lots of value pairs. — Steve Kim
– Steve Kim, Commented Feb 7, 2017 at 7:38
Lots of value pairs or only 3 (in the question you have mentioned max 3 values)? Is your key always going to be integer? — Vivek Athalye
– Vivek Athalye, Commented Feb 7, 2017 at 7:42

Suren Srapyan · Accepted Answer · 2017-02-07 08:02:02Z

2

You can use remainder operator and number % 3 in the property, if your number will change it's value by 1.

number % 3 - this will keep your index from 0 up to 2. So if you enter the 4th element, it's index will be 4 % 3 === 1, if you starts from 1.

var car= {};
car[number % 3] = user_input;

Example

var car= [];
var number = 0;
var input;

while(number < 10){
  input = prompt();
  car[number % 3] = input;
  console.log(car);
  number++;
}

With ids you can store them and use the number to get the appropriate one.

var ids = [234, 4641, 1352];

var car= {};
var number = 0;
var input;
var ids = [234, 4641, 1352];

while(number < 10){
  input = prompt();
  car[ids[number % 3]] = input;
  console.log(car);
  number++;
}

edited Feb 7, 2017 at 8:02

answered Feb 7, 2017 at 7:38

Suren Srapyan

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6 Comments

Suren Srapyan Over a year ago

@steveKim see. Edited

Steve Kim Over a year ago

Thank you for the great information. Just a quick question. Let say the key is not 0-2 number, but rather an id (such as "234", "4641" or "1352"). So the key is not from 0 to 2, but rather a random number. In this case, how would I apply the same concept?

Suren Srapyan Over a year ago

Here we choose our indexes from the number. With the id's it must be changed. For every time your id's are different or they stay the same

Nina Scholz Over a year ago

@steveKim, if the given keys are necessary, please add this information to the question above.

Pritam Banerjee Over a year ago

Same comment: Why do you need the index count? OP says that the user will input the index number?

|

Nina Scholz · Accepted Answer · 2017-02-07 07:55:53Z

2

You could use the remainder operator % and move the value into the range. Then add one for the one based interval.

var car = {},
    insertCar = function (index) {
        return function (carName) {
            car[index + 1] = carName;
            index++;
            index %= 3;
        }
    }(0);


insertCar('Fiat');
console.log(car);
insertCar('Honda');
console.log(car);
insertCar('Ford');
console.log(car);
insertCar('Nissan');
console.log(car);
insertCar('Tesla');
console.log(car);

.as-console-wrapper { max-height: 100% !important; top: 0; }

With give keys [234, 4641, 1352] and round robin

var car = {},
    insertCar = function (index) {
        var keys = [234, 4641, 1352];
        return function (carName) {
            car[keys[index]] = carName;
            index++;
            index %= keys.length;
        }
    }(0);


insertCar('Fiat');
console.log(car);
insertCar('Honda');
console.log(car);
insertCar('Ford');
console.log(car);
insertCar('Nissan');
console.log(car);
insertCar('Tesla');
console.log(car);

.as-console-wrapper { max-height: 100% !important; top: 0; }

With an array, as suggested

var car = [],
    insertCar = function (index) {
        return function (carName) {
            car[index] = carName;
            index++;
            index %= 3;
        }
    }(0);


insertCar('Fiat');
console.log(car);
insertCar('Honda');
console.log(car);
insertCar('Ford');
console.log(car);
insertCar('Nissan');
console.log(car);
insertCar('Tesla');
console.log(car);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Feb 7, 2017 at 7:55

answered Feb 7, 2017 at 7:43

Nina Scholz

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2 Comments

Pritam Banerjee Over a year ago

Why do you need the index count? OP says that the user will input the index number?

Nina Scholz Over a year ago

@PritamBanerjee, the op does not know, what to use. a comment shows, that possible an array of keys is used ... but who knows.

Pritam Banerjee · Accepted Answer · 2017-02-07 07:44:24Z

0

You can use something like this:

var carCount = "Take this as UserInput";
var newValue = "Take the value as Input as well"

if (carCount < 3){
  (car[carCount] = newValue);
}

answered Feb 7, 2017 at 7:44

Pritam Banerjee

19.1k10 gold badges97 silver badges113 bronze badges

2 Comments

Steve Kim Over a year ago

I upvoted. It's simple but I can see how it can be used. I am not sure who downvoted.

Pritam Banerjee Over a year ago

@steveKim If you liked my answer can you please accept the answer? Thanks

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