Adding text to beginning of Object property value

Question

Hi there I am adding the string 'a ' to the beginning of the value of name. I have also added a condition where if the value of name.length === 3, then add the string 'a ' but it is only returning the objects that get changed and only the name property.

var values1 = [
  {
    name: 'dog',
    surname: 'good',
    skills: 'programming',
  },
  {
    name: 'cat',
    surname: 'soft',
    skills: 'engineer',
  },
  {
    name: 'elephant',
    surname: 'big',
    skills: 'programming',
  },
];

let array = [];
for (let i = 0; i < values1.length; i++) {
  if (values1[i]['name'].length == 3) {
    array.push({ name: 'a ' + values1[i]['name'] });
  }
}

for (let i = 0; i < array.length; i++) {
  console.log(array[i]);
}

This is the result I would like to return.

[
  {
    name: 'a dog',
    surname: 'good',
    skills: 'programming',
  },
  {
    name: 'a cat',
    surname: 'soft',
    skills: 'engineer',
  },
  {
    name: 'elephant',
    surname: 'big',
    skills: 'programming',
  },
];

What is your question? Do you mean 'Result in Terminal' is the result you would like to achieve? — pilchard
– pilchard, Commented Dec 10, 2021 at 20:10
I am not the best at explaining, but if you look at the console.logged result, its essentially what I want — noobdev123
– noobdev123, Commented Dec 10, 2021 at 20:15
You're actually quite close, but review if this line makes sense: array.push({ name: 'a ' + values1[i]['name'] }); — ᴓᴓᴓ
– ᴓᴓᴓ, Commented Dec 10, 2021 at 20:19

pilchard · Accepted Answer · 2021-12-10 22:10:48Z

1

You're quite close, but instead of adding a name key (push()) you want to reassign the value of the name field.

var values1 = [
  {
    name: 'dog',
    surname: 'good',
    skills: 'programming',
  },
  {
    name: 'cat',
    surname: 'soft',
    skills: 'engineer',
  },
  {
    name: 'elephant',
    surname: 'big',
    skills: 'programming',
  },
];

for (let i = 0; i < values1.length; i++) {
  if (values1[i]['name'].length == 3) {
    values1[i]['name'] = 'a ' + values1[i]['name'];
  }
}

console.log(values1)

I modified the existing array rather than adding a new one. I don't think it's dangerous as we are updating a primitive.

edited Dec 10, 2021 at 22:10

pilchard

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answered Dec 10, 2021 at 20:21

ᴓᴓᴓ

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2 Comments

pilchard Over a year ago

This mutates the array in place, which it looks like the OP was trying to avoid.

ᴓᴓᴓ Over a year ago

I do mention that ('modified the existing array'), but it wasn't mentioned in the post, so I assumed it was just because they didn't see how to mutate it in place. If that's a requirement it's a fairly easy change. edit: I think your answer is overall better due to the explanation, but I wanted to provide one as well to help OP see where they went wrong.

pilchard · Accepted Answer · 2021-12-10 20:29:36Z

1

Here is an example using map() and destructuring the name property in the callback.

var values1 = [
  { name: 'dog', surname: 'good', skills: 'programming' },
  { name: 'cat', surname: 'soft', skills: 'engineer' },
  { name: 'elephant', surname: 'big', skills: 'programming' },
];

const result = values1.map(({ name, ...rest }) => 
  ({ name: (name.length === 3 ? `a ${name}` : name), ...rest }));

console.log(result);

But to make your code work you simply need to be sure to push the whole object regardless of whether the name is changed or not. Here creating a copy of the object using Object.assign() updating the name if needed, then pushing the copy to the array.

var values1 = [
  {
    name: 'dog',
    surname: 'good',
    skills: 'programming',
  },
  {
    name: 'cat',
    surname: 'soft',
    skills: 'engineer',
  },
  {
    name: 'elephant',
    surname: 'big',
    skills: 'programming',
  },
];

let array = [];
for (let i = 0; i < values1.length; i++) {
  const obj = Object.assign({}, values1[i]);

  if (obj['name'].length === 3) {
    obj.name = 'a ' + obj['name'];
  }

  array.push(obj);
}

for (let i = 0; i < array.length; i++) {
  console.log(array[i]);
}

edited Dec 10, 2021 at 20:29

answered Dec 10, 2021 at 20:19

pilchard

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2 Comments

noobdev123 Over a year ago

I am trying to avoid ...rest as this code is used at a bigger scale. I just asked this question for a simple reasons

pilchard Over a year ago

The second example doesn't use ...rest but it does clone the objects using spread.

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