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JavaScript Function Object

In JavaScript, functions are called Function Objects because they are objects.

In JavaScript, the purpose of Function constructor is to create a new Function object. 

Just like objects, functions have properties and methods, they can be stored in a variable or an array, and be passed as arguments to other functions.


As all other objects, Function objects can be created using the new operator as shown below.

new Function ([arg1[, arg2[, ....argn]],] functionBody)

arg1, arg2, …. , argn – It represents the argument used by function. Zero or more names to be used by the function as formal parameters. Each must be a proper JavaScript identifier.

functionBody – It represents the function definition. A string containing the JavaScript statements comprising the function body.

Using the Function constructor to create functions is not recommended since it needs the function body as a string which may prevent some JS engine optimizations and can also cause other problems.


var add=new Function("num1","num2","return num1+num2");  
document.writeln(add(2,5));  //Output will be 7

Function Properties

Javascript Function.length: Returns the number of parameters of a function.

Javascript Returns the name of the given function.

Function Methods

apply()It is used to call a function contains this value and a single array of arguments.
bind()It is used to create a new function.
call()It is used to call a function contains this value and an argument list.
toString()It returns the result in a form of a string.
Function Methods