To sort JavaScript array by two numeric fields, we call the sort method.
For instance, we write
const sorted = grouperArray.sort((a, b) => {
return a.size - b.size || a.glow - b.glow;
});
to call sort with a callback that compares the items by their size property values and glow property values.
To upload multiple files using JavaScript formData, we call append with an array key.
For instance, we write
fd.append("fileToUpload[]", document.getElementById("fileToUpload").files[0]);
to call fd.append with the "fileToUpload[]" array key and a file we get from a file input.
We get the file input with getElementById.
And we get the selected files from the files property.
To sort a JavaScript array based on the length of each element, we call the sort method.
For instance, we write
const sorted = arr.sort((a, b) => {
return b.length - a.length;
});
to call arr.sort with a callback that subtracts the length property values of b and a to return an array with the strings in arr sorted by length in descending order.
To remove first and last element in a JavaScript array, we use shift to remove the first item and pop to remove the last item.
For instance, we write
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift();
fruits.pop();
to call fruits.shift to remove the first item from fruits.
And we call fruits.pop to remove the last item from fruits.
To reorder arrays with JavaScript, we can use destructuring syntax.
For instance, we write
const swapPositions = (array, a, b) => {
[array[a], array[b]] = [array[b], array[a]];
};
let array = [1, 2, 3, 4, 5];
swapPositions(array, 0, 1);
to define the swapPositions function that assigns array[b] to array[a] and array[a] to array[b] with destructuring to swap the positions of the array entries at indexes a and b.
Then we call it with the array and the positions we want to swap.