Category: JavaScript Answers

To add default array values with JavaScript, we call the fill method.

For instance, we write

const arr = Array(100).fill(0);

to define an array with 100 empty slots with Array(100).

Then we call fill with 0 to fill the empty slots with 0’s.

To declare an array in JavaScript, we use array literals.

For instance, we write

const x = [];
const y = [10];

const z = [];
z[2] = 12;

to declare array x which is an empty array.

We declare y which is an array with 10 in it.

And we declare array z as an empty array and then set 12 as the 3rd element in z.

To count the number of times a same value appears in a JavaScript array, we call the filter method.

For instance, we write

const getOccurrence = (array, value) => {
  return array.filter((v) => v === value).length;
};

console.log(getOccurrence(arr, 1));

to call array.filter with a callback that checks if v in array equals to value.

An array of values in array that equals to value is returned.

Then we get the count using the length property.

To use promise in forEach loop of array to populate an object with JavaScript, we use Promise.all with an array of promises.

For instance, we write

const promises = array.map(async (element) => {
  const data = await developer.getResources(element);
  name = data.items[0];
  const response = await developer.getResourceContent(element, file);
  fileContent = atob(response.content);
  files.push({
    fileName,
    fileType,
    content,
  });
});

await Promise.all(promises);

to call array.map with an async function which returns a promise.

Therefore, promises is an array of promises.

And we call Promise.all with promises to return a promise that resolves when all the promises are resolved.

The promises are run in parallel.

To append an array to form data in JavaScript, we call the append method.

For instance, we write

formData.append("tags", JSON.stringify(tags));

to call formData.append with the key and value of the entry.

The value is an array converted to a JSON string with JSON.stringify.