To move item in array to last position with JavaScript, we use the splice method.
For instance, we write
const a = [1, 2, 5, 4, 3];
a.splice(4, 0, a.splice(2, 1)[0]);
console.log(a);
to remove the 3rd element from the array and return it in an array with a.splice(2, 1).
We get the removed item with index 0.
And then we put it after index 4 by calling splice again with 4, 0, and a.splice(2, 1)[0].
To delete property from spread operator with JavaScript, we use the rest syntax.
For instance, we write
const myObject = {
a: 1,
b: 2,
c: 3,
};
const { b, ...noB } = myObject;
console.log(noB);
to use the rest syntax to get all the properties except b from myObject.
b is destructured earlier, so it’ll be omitted from noB.
To create an associative array in JavaScript literal notation, we can create a map.
For instance, we write
const arr = new Map([
["key1", "User"],
["key2", "Guest"],
["key3", "Admin"],
]);
const res = arr.get("key2");
console.log(res);
to create an associative array with the Map constructor.
Then we call get with the key to get the value associated with the key.
To get the length of a JavaScript associative array, we use the Object.keys method.
For instance, we write
const quesArr = {};
quesArr["q101"] = "Your name?";
quesArr["q102"] = "Your age?";
quesArr["q103"] = "Your school?";
console.log(Object.keys(quesArr).length);
to call Object.keys to get the property keys of quesArr in an array.
Then we use the array’s length property to get the length of the associative array.
To add items to an object with JavaScript, we assign the value to a property.
For instance, we write
const sendData = { field1: value1, field2: value2 };
sendData.field3 = value3;
to define the sendData object.
And then we set the field3 property to value3.