Javascript methods advanced leves with example

1. Array.prototype.reduce()

The reduce method executes a reducer function on each element of the array, resulting in a single output value.

Example: Summing an array of numbers

ja
const numbers = [1, 2, 3, 4, 5];
const sum = numbers.reduce((accumulator, currentValue) => accumulator + currentValue, 0);
console.log(sum); // Output: 15

2. Array.prototype.flat()

The flat method creates a new array with all sub-array elements concatenated into it recursively up to the specified depth.

Example: Flattening a nested array

javascrip
const nestedArray = [1, [2, [3, 4]], 5];
const flattened = nestedArray.flat(2);
console.log(flattened); // Output: [1, 2, 3, 4, 5]

3. Promise.all()

The Promise.all() method takes an iterable of Promise objects and, when all of the promises have resolved, returns a single Promise that resolves with an array of the results.

Example: Fetching multiple resources

javascrip
const fetchData1 = () => Promise.resolve('Data 1');
const fetchData2 = () => Promise.resolve('Data 2');

Promise.all([fetchData1(), fetchData2()])
  .then(results => console.log(results)) // Output: ['Data 1', 'Data 2']
  .catch(error => console.error(error));

4. Object.entries()

The Object.entries() method returns an array of a given object's own enumerable string-keyed property [key, value] pairs.

Example: Converting an object to an array of entries

javascript
const obj = { a: 1, b: 2, c: 3 };
const entries = Object.entries(obj);
console.log(entries); // Output: [['a', 1], ['b', 2], ['c', 3]]

5. String.prototype.includes()

The includes method determines whether one string can be found within another string, returning true or false as appropriate.

Example: Checking for a substring

javascr
const str = 'Hello, world!';
const hasHello = str.includes('Hello');
console.log(hasHello); // Output: true

6. Set()

A Set is a collection of values where each value must be unique. It can be used to remove duplicates from an array.

Example: Removing duplicates

javascript
const numbers = [1, 2, 2, 3, 4, 4, 5];
const uniqueNumbers = [...new Set(numbers)];
console.log(uniqueNumbers); // Output: [1, 2, 3, 4, 5]

7. Function.prototype.bind()

The bind method creates a new function that, when called, has its this keyword set to the provided value.

Example: Setting context for a method

javascript
const obj = { value: 42 };
function getValue() {
  return this.value;
}
const boundGetValue = getValue.bind(obj);
console.log(boundGetValue()); // Output: 42

8. Array.prototype.find()

The find method returns the value of the first element in the array that satisfies the provided testing function.

Example: Finding an object in an array

javasll
const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];
const user = users.find(u => u.id === 2);
console.log(user); // Output: { id: 2, name: 'Bob' }

9. Array.prototype.sort()

The sort method sorts the elements of an array in place and returns the sorted array. It can accept a comparison function for custom sorting.

Example: Sorting an array of numbers

javas
const arr = [4, 2, 5, 1, 3];
arr.sort((a, b) => a - b);
console.log(arr); // Output: [1, 2, 3, 4, 5]

10. Array.prototype.some()

The some method tests whether at least one element in the array passes the test implemented by the provided function.

Example: Checking for at least one eve number

javas
const numbers = [1, 3, 5, 7, 8];
const hasEven = numbers.some(num => num % 2 === 0);
console.log(hasEven); // Output: true

These methods can help you write more efficient and readable JavaScript code. If you want more examples or explanations on specific methods, feel free to ask!