A JavaScript function is a block of code designed to perform a particular task.
1)Function Definition
–>Before we use a function, we need to define it.
–>A function definition (also called a function declaration, or function statement) consists of the function keyword, followed by:
The name of the function.
–>A list of parameters to the function, enclosed in parentheses and separated by commas.
–>The JavaScript statements that define the function, enclosed in curly brackets, {…}.
Example:
//Function Definition
function sum(){
var a = 10, b = 40;
var total = a+b;
console.log(total);
}
2)Calling functions
–>Defining a function does not execute it.
–>A JavaScript function is executed when “something” invokes it (calls it).
Example:
function sum(){
var a = 10, b = 40;
var total = a+b;
console.log(total);
}
sum(); //function call
3)Function Parameter vs Function Arguments
–>Function parameters are the names listed in the function’s definition.
–>Function arguments are the real values passed to the function.
Example:
function sum(a,b){
var total = a+b;
console.log(total);
}
sum();
sum(20,30);
sum(50,50);
sum(5,6)
output:
PS C:UsersThe-BeastDesktopjavascript Blog> node index.js
NaN
50
100
11
PS C:UsersThe-BeastDesktopjavascript Blog>
4)Function expressions
“Function expressions simply means create a function and put it into the variable “
Example:
function sum(a,b){
var total = a+b;
console.log(total);
}
var funExp = sum(5,15);
output:
PS C:UsersThe-BeastDesktopjavascript Blog> node index.js
20
PS C:UsersThe-BeastDesktopjavascript Blog>
5) Return Keyword
When JavaScript reaches a return statement, the function will stop executing.
The return value is “returned” back to the “caller”.
Example:
function sum(a,b){
return total = a+b;
}
var funExp = sum(5,25);
console.log('the sum of two no is ' + funExp );
output:
PS C:UsersThe-BeastDesktopjavascript Blog> node index.js
the sum of two no is 30
PS C:UsersThe-BeastDesktopjavascript Blog>
6) Anonymous Function
A function expression is similar to and has the same syntax as a function declaration One can define “named”.function expressions (where the name of the expression might be used in the call stack for example) or “anonymous” function expressions.
Example:
var funExp = function(a,b){
return total = a+b;
}
var sum = funExp(15,15);
var sum1 = funExp(20,15);
console.log(sum);
console.log(sum1);
output:
PS C:UsersThe-BeastDesktopjavascript Blog> node index.js
30
35
PS C:UsersThe-BeastDesktopjavascript Blog>
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