Utilize Array.filter to retrieve specific values based on a defined number of elements

I have a function that currently retrieves the url value for each item in an array up to a specified maximum number. Below is the code snippet:

const myArray = [
    { url: "example.com/1", other: "foo" },
    { url: "example.com/sdf", other: "foo"  },
    { url: "example.com/blue", other: "foo"  },
    { url: "example.com/foo", other: "foo"  },
    { url: "example.com/123", other: "foo"  },
];

function getNumberOfUrls(data, num) {
  const newArray = [];

  data?.forEach(function (datum) {
    if (newArray.length < num) {
      newArray.push(datum.url);
    }
  });

  return newArray;
}

// Output
//["example.com/1", "example.com/sdf", "example.com/blue"] 

The current function works as expected but I am considering if there is a more suitable Array method for this task.

I am aware that Array.filter creates a new array based on a specific condition and I was wondering if it could be utilized to check another condition, specifically related to the parent array.

function getNumberOfUrls(data, num) {
  return data.filter(datum => /* How can we return the url until .length === num in the data? */ )
};

Is there a way to implement this or are there better-suited Array methods for achieving this goal?

ETA: The provided example array may not fully illustrate the issue. Additional data has been added to clarify. The objective is to extract only the url values from the first three objects in the array instead of returning an array with those objects.

Answer №1

If you want a quick solution, you can utilize the Array.slice method:

const myArray = [
  { url: "example.com/1" },
  { url: "example.com/sdf" },
  { url: "example.com/blue" },
  { url: "example.com/foo" },
  { url: "example.com/123" },
]

const limit = 3
const shorterArray = myArray.slice(0, limit).map(item => item.url)

console.log(shorterArray)

I opted to remove my previous code as it was not efficient and should be avoided.

Answer №2

Using Array.from() along with its internal mapper can be a useful approach

const myArray = [
    { url: "example.com/1" },
    { url: "example.com/sdf" },
    { url: "example.com/blue" },
    { url: "example.com/foo" },
    { url: "example.com/123" },
];

function getNumberOfUrls(data, num) {
  return Array.from({length:num}, (v,i) => data[i].url)
}

console.log(getNumberOfUrls(myArray, 3))

Answer №3

To adjust the length of the newly transformed array, you can simply set it

Update: The .map() function is utilized to create a new array with only URLs from the original array

const myArray = [
    { url: "example.com/1" },
    { url: "example.com/sdf" },
    { url: "example.com/blue" },
    { url: "example.com/foo" },
    { url: "example.com/123" },
];

function getNumberOfUrls(data, num) {
  
  let newArray = data.map(el => el.url);
  newArray.length = num;

  return newArray;
}

console.log(getNumberOfUrls(myArray, 3))

Answer №4

If you have a JavaScript array, how can you extract only the first X items from it?

You can achieve this by using the built-in slice() method that every array instance provides: (Please note that the original array remains unchanged during this operation.)

const myArray = [
{ url: "example.com/1", other: "foo" },
{ url: "example.com/sdf", other: "foo"  },
{ url: "example.com/blue", other: "foo"  },
{ url: "example.com/foo", other: "foo"  },
{ url: "example.com/123", other: "foo"  },
];

const limit = 3 //extract the first 3 items

const newArray = myArray.slice(0,limit).map( (item) => {return {url:item.url} })
console.log(newArray)
 

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