To use map() on an array in reverse order with JavaScript, we make a copy before we reverse the array.
For instance, we write
myArray
.slice(0)
.reverse()
.map((a) => {
//...
});
to call slice to make a copy of myArray and return it.
And then we call reverse to reverse the copied array.
Then we call map to map the entries of the reversed array.
To unpack array into separate variables in JavaScript, we use destructuring.
For instance, we write
const arr = ["one", "two"];
const [one, two] = arr;
to assign the entries in arr into their own variables with the destructuring syntax.
So one is 'one' and two is 'two'.
To check if two arrays have the same values with JavaScript, we sort them before comparing them.
For instance, we write
const array1 = [
10, 6, 19, 16, 14, 15, 2, 9, 5, 3, 4, 13, 8, 7, 1, 12, 18, 11, 20, 17,
];
const array2 = [
12, 18, 20, 11, 19, 14, 6, 7, 8, 16, 9, 3, 1, 13, 5, 4, 15, 10, 2, 17,
];
if (array1.sort().join(",") === array2.sort().join(",")) {
console.log("same members");
}
to call sort to sort the numbers in the arrays and then we call join to join the entries with commas to form a string.
Then we compare them with === to see if they’re the same.
To convert JavaScript array to a string, we use the JSON.stringify method.
For instance, we write
const a = ["a", "b", "c"];
const str = JSON.stringify(a);
to call JSON.stringify with a to convert the a array to a JSON string.
To convert base64 string to ArrayBuffer with JavaScript, we use the Buffer.from method.
For instance, we write
const myBuffer = Buffer.from(someBase64String, "base64");
to call Buffer.from with the someBase64String base64 string and 'base64' to convert the base 64 string to a buffer.