JAVASCRIPT
JS COMMENTS
*It is most important in java script.
*It is used to explain the java script code.
Single line comments
* Single line comments start with //.
*Any text between // and the end of the line will be ignored by JavaScript.
Example
Multiple line comments
*Multi-line comments start with /* and end with */.
*Any text between /* and */ will be ignored by JavaScript.
Example
Variables
Example
In this example, x, y, and z, are variables, declared with the let keyword:
Operators
assignment operator
*The assignment operator (=) assigns a value to a variable.
Example
addition operator
*The addition operator (+) adds numbers:
Example
String operator
Logical operator
&& AND gate
|| OR gate
! NOT gate
AND gate
*It is the strict gate, It will pass only whether the 2 statement is pass
0 && 0 = 0
0 && 1 = 0
1 && 0 =0
1 && 1 = 1
OR gate
* It will pass whether the 1 statement is pass
0 || 0 = 0
0 || 1 = 1
1 || 0 = 1
1 || 1 = 1
Examples
* In this line we want to see whether the two condition is right.
* First we saw x is greater than 2 and y is smaller than 5.
* In this case x is greater than 2 and y is not less than 5, So it is false.
Datatypes
Strings
(let doll = "It's alright";)
Numbers
Let x=2;
Boolean
Booleans can only have two values: true or false.
Array
If you have a list of items , storing the cars in single variables.
if you want to loop through the cars and find a specific one? And what
if you had not 3 cars, but 300?
The solution is an array!
An array can hold many values under a single name, and you can
access the values by referring to an index number.
Example
Object
In real life, a car is an object.
A car has properties like weight and colour, and methods like start and stop:
All cars have the same properties, but the property values differ from car to car.
Functions
A JavaScript function is a block of code designed to perform a particular task.
A JavaScript function is executed when "something" invokes it (calls it).
Example
If/Else
Conditional statements are used to perform different actions based on different conditions.
Use if to specify a block of code to be executed, if a specified condition is true
Use else to specify a block of code to be executed, if the same condition is false
Use else if to specify a new condition to test, if the first condition is false
Example
Switch
* The value of the expression is compared with the values of each case.
* If there is a match, the associated block of code is executed.
* If there is no match, the default code block is executed.
Example
For loop
loops through a block of code a number of times.
Statement 1: sets a variable before the loop starts (let i = 0).
Statement 2 : defines the condition for the loop to run (i must be less than 5).
Statement 3 : increases a value (i++) each time the code block in the loop has been executed.
Example
Map
*We set the value of the key in a map
*We get the value of a key in a map
Example