Question 296721 in Javascript Question posted in
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Javascript – How can i cut a string property of a object in a array?

I would like to know if there is a way to access the "description" property of the objects within the array and use some string cutting method, such as slice, returning an array of objects with the value of this property already modified. I tried with some for loops but I didn’t get the result.

the code:

let cars = [
  {
    "status": "disabled"
  },
  
  {
    "status": "active",
    "store": true,
    "models": [
        {
          "description": "4 doors, 0km/h, no breakdowns",
          "color": "black",
          "price": 100.000,
        },
        {
          "description": "2 doors, 30.000km/h, some breakdowns",
          "color": "black",
          "price": 20.000,
        },
      
        {
          "description": "4 doors, 120.000km/h, no breakdowns",
          "color": "red",
          "price": 50.000,
        }
    ]
  }
]

I can get the property I want and use slice() inside a for loop to cut it, but I’m having difficulty returning this array of objects when i call "carsTwo" with the information already modified. Here’s what i’ve done:

let carsTwo= cars[1].models;

//here i'm deleting the propreties that i don't want to return in my new array
for(let i=0; i<carsTwo.length; i++) {
    delete carsTwo[i].color;
    delete carsTwo[i].price;
}

//here i'm trying to apply slice() in every "description" property value, and it works but only in console.log...
for(let i=0; i<carsTwo.length; i++) {
    carsTwo[i].description.slice(3)
}

my goal is to return the array of objects only containing description property, with the slice applied.

obs: i’m a beginner.

Tags:

3

Answers


  1. 0

    I think you are looking for something like this:

    function cutCarsDescription(cars, index) {
    for(let i = 0; i < cars.length; i++) {
        const car = cars[i]
        if(car.models) {
            for(let j = 0; j < car.models.length; j++) {
                const model = car.models[j]

                model.description = model.description.slice(0, index)
            }
        }
    }
}

    Just path cars as the 1st argument and index of slicing as the 2nd

    It will modify your cars array, so you don’t need to return anything from function

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  2. 0

    .slice() returns the new string, it doesn’t modify the string in place, so you’d need to update your .description property on the object to assign it to the new string that slice() returns:

    carsTwo[i].description = carsTwo[i].description.slice(3);

    const cars = [
  {
    "status": "disabled"
  },
  
  {
    "status": "active",
    "store": true,
    "models": [
        {
          "description": "4 doors, 0km/h, no breakdowns",
          "color": "black",
          "price": 100.000,
        },
        {
          "description": "2 doors, 30.000km/h, some breakdowns",
          "color": "black",
          "price": 20.000,
        },
      
        {
          "description": "4 doors, 120.000km/h, no breakdowns",
          "color": "red",
          "price": 50.000,
        }
    ]
  }
];

const carsTwo = cars[1].models;

for(let i=0; i<carsTwo.length; i++) {
    delete carsTwo[i].color;
    delete carsTwo[i].price;
}

for(let i=0; i < carsTwo.length; i++) {
    carsTwo[i].description = carsTwo[i].description.slice(3);
}

console.log(carsTwo);

    Note the above about your code above:

    • You have two for loops one after another that both loop the same amount of times. These should be merged together to avoid doing an additional iteration of your items:

      for(let i=0; i<carsTwo.length; i++) {
  delete carsTwo[i].color;
  delete carsTwo[i].price;
  carsTwo[i].description = carsTwo[i].description.slice(3);
}

    • By using operations such as delete and updating the original object by reassigning .description, you’re updating the objects in your original array, which may not be desirable (you can see this if you print your cars array after the above code).

    To avoid updating your original array, I would suggest creating a new array and adding new objects with the description property instead of modifying your existing array of objects. This can be done by using .map() to transform each object in your models array to a new array of objects, that way you’re not updating the original objects, keeping the original cars array untouched:

    const cars = [ { "status": "disabled" }, { "status": "active", "store": true, "models": [ { "description": "4 doors, 0km/h, no breakdowns", "color": "black", "price": 100.000, }, { "description": "2 doors, 30.000km/h, some breakdowns", "color": "black", "price": 20.000, }, { "description": "4 doors, 120.000km/h, no breakdowns", "color": "red", "price": 50.000, } ] } ];

// Using "destructuring assignment" to pull out the models array from the second object in your array
const [, { models }] = cars;

const res = models.map((model) => ({description: model.description.slice(3)}));
console.log(res);
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  3. 0

    It is possible to do in a quite concise manner by using Array.map():

    const cars = [ { "status": "disabled" }, { "status": "active", "store": true, "models": [ { "description": "4 doors, 0km/h, no breakdowns", "color": "black", "price": 100.000, }, { "description": "2 doors, 30.000km/h, some breakdowns", "color": "black", "price": 20.000, }, { "description": "4 doors, 120.000km/h, no breakdowns", "color": "red", "price": 50.000, } ] } ];
const carsTwoModified = cars[1].models.map((model) => ({ description: model.description.slice(3) }));

console.log(carsTwoModified);
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