Javascript advance feature like spread syntax , callback, object, object.assign, object.freeze , obbject.seal, map(), reducer(), filter(), forEach() function.

1. JAVASCRIPT
TAREK RAIHAN
EMAIL : TAREKRAIHAN@YAHOO.COM

2. THE SPREAD SYNTAX (…)
• Use of spread syntax (…)
• Inserting Arrays
• Math
• Copy an Array
• String to Array

3. # INSERTING ARRAY

4. # MATH FUNCTION

5. # COPY AN ARRAY

6. # COPY AN ARRAY

7. # STRING TO ARRAY

8. CALLBACK
• A callback is a function that is to be executed after another
function has finished executing — hence the name ‘call back’.
• In JavaScript, functions are objects. Because of this, functions
can take functions as arguments, and can be returned by other
functions. Functions that do this are called higher-order
functions. Any function that is passed as an argument is called
a callback function.

9. WHY DO WE NEED CALLBACKS?
• JavaScript is an event driven language. This means that instead
of waiting for a response before moving on, JavaScript will keep
executing while listening for other events

10. CREATE A CALLBACK

11. CREATE A CALLBACK

12. # OBJECT
• An object is a dynamic collection of properties
• The property key is a unique string. When a non string is used
as the property key, it will be converted to a string. The
property value can be a primitive, object, or function.
• The simplest way to create an object is to use an object literal:

13. OBJECT ACCESS PROPERTY
• There are two ways to access properties: dot notation and
bracket notation. We can read, add, edit and remove an object’s
properties at any time.
• Get : object.name or object[expression]
• Set : object.name = “Tarek” or object[expression] = “Tarek”
• Delete : delete object.name or delete object[expression]

14. OBJECT METHODS
• Object.assign() copies all properties from one object to
another. An object can be cloned by copying all its properties
to an empty object:
• Merging objects

15. OBJECT METHODS
• Object.freeze() method freezes an object. A frozen object can
no longer be changed;

16. OBJECT METHODS
The Object.seal() method seals an object, preventing new properties from being added to
it and marking all existing properties as non-configurable. Values of present properties
can still be changed as long as they are writable.

17. MAP, FOREACH, FILTER, REDUDE
• forEach() -executes a provided function once for each array element. It replace original
object.
• Map() - creates a new array with the results of calling a provided function on every
element in the calling array.
• let arr = [1,2,3,4];
• let plus5 = arr.map((val, i, arr) => {
• return val + 5;
• });
• // plus5 = [5, 7, 8, 9]
• The filter() method returns a new array created from all elements that pass a certain test
preformed on an original array.
• let arr = [1,2,3,4,5,6];
• let even = arr.filter(val => {
• return val % 2 === 0;
• });
• // even = [2,4,6]
• The reduce() method is used to apply a function to each element in the array to reduce
the array to a single value.
• let arr = [1,2,3,4];
• let sum = arr.reduce((acc, val) => {
• return acc + val;

18. LINKS
https://codeburst.io/javascript-what-the-heck-is-a-callback-aba4da2deced
https://medium.com/@cristiansalcescu/learn-these-javascript-fundamentals-and-
become-a-better-developer-2a031a0dc9cf
https://medium.com/free-code-camp/write-less-do-more-with-javascript-es6-
5fd4a8e50ee2
https://codeburst.io/javascript-map-vs-foreach-f38111822c0f
https://codeburst.io/javascript-learn-to-chain-map-filter-and-reduce-acd2d0562cd4
https://codeburst.io/learn-understand-javascripts-filter-function-bde87bce206
https://codeburst.io/learn-understand-javascripts-reduce-function-b2b0406efbdc
https://medium.com/@dis_is_patrick/practical-uses-for-closures-c65640ae7304
https://medium.com/dailyjs/i-never-understood-javascript-closures-9663703368e8
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures
https://developer.mozilla.org/en-
US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze
https://developer.mozilla.org/en-
US/docs/Web/JavaScript/Reference/Global_Objects/Object/seal

20. THANK
YOU