Introduction
This webpage is a continuation of a beginner's guide to JavaScript and covers topics such as data types, conditional statements, loops, and functions.
What are Basic operators?
Basic operators are addition +
, multiplication *
, subtraction -
, Division /
, Remainder %
, Exponentiation **
.and so on. For example:
alert( 5 % 2 ); // 1, a remainder of 5 divided by 2 //Remainder operator
alert( 2 ** 2 ); // 4 (2 multiplied by itself 2 times) //Exponentiation operator
What is String concatenation? String concatenation means merging/connecting two strings with the plus operator '+'.
For Example:
let str = "my" + "string";//alert(str); // mystring
alert( '1' + 2 ); // "12"
alert( 2 + '1' ); // "21"
alert(2 + 2 + '1' ); // "41" here firstly two numbers are added then 4 is converted to string then, adds string '4' to string '1'.
From this above example, we can understand that string '1' tries to convert number 2 to string and adds 12 whereas "21" is also the same 2 is converted at the string and added with string '1' and so on.
Rules of '+=' and '*=' operators:
let n = 2;
n += 5; // n = 7 operator + is calculated first like 2+5=7.
n *= 2; // n = 14 now value of 'n' is 7 so 7*2=14.
alert( n ); // 14
How are Increment/decrement operations done?
Increment++ increases a variable by '1'. Decrement-- decreases a variable by '1'.
For Example:
let counter = 2;
counter++; // 2+1=3 increment by '1'.
alert( counter ); // returns 3
let counter = 2;
counter--; //2-1=1 decrement by '1'.
alert( counter ); // 1
let a = 1, b = 1;
alert( ++a ); // 2, prefix form returns the new value
alert( b++ ); // 1, postfix form returns the old value
alert( a ); // 2, incremented once
alert( b ); // 2, incremented once
What are comparison operators?
Comparison operators are those operators which are used for comparing two operands.
1. a > b, a < b // greater than less then operators.
2. a >= b, a <= b // greater/less then equal to.
3. a == b // eqality test.
4. a = b // assigning value 'a' to value 'b'.
5. a != b // 'a' is not equal to 'b'.
6. a === b //strict operator
Simple Example:
alert( 2 > 1 ); // true
alert( 2 == 1 ); // false
alert( 2 != 1 ); // true
What is Conditional branching?
conditional branching is the term used to describe operations such as 'if(condition)', 'else(condition)', 'else if', and 'if else' by using different operators.
For Example:
let year = prompt('In which year was the ECMAScript-2015 specification published?', '');
if (year < 2015) {
alert( 'Too early...' );
} else if (year > 2015) {
alert( 'Too late' );
} else {
alert( 'Exactly!' );
}
In the code above, JavaScript first checks year < 2015. If that is false, it goes to the next condition year > 2015. If that is also false, it shows the last alert. There can be more else if blocks. The final else is optional.
Note: A number 0, an empty string `""`
, null, undefined, and NaN all become false. Because of that, they are called “falsy” values. Other values become true, so they are called “truthy”.
What are logical operators?
Logical operators are '|| (OR), && (AND), ! (NOT)'.