Hoisting in javascript?
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Variable and function declarations are hoisted to the top of the function scope.
In detail:
The flow of execution of program is known as execution context.
Global code –Initial section of program execution is known as global code.
Function code – Once the execution enters into a function call.
<script>
var a=”Global execution”; // Global context
function myfun(){
var b=”Global execution”;
}
myfun(); // Functional context
</script>
Execution Context Stack
JavaScript interpreter in a browser is known as Execution Context Stack.
Each function call creates a new execution context.
So once a new function called , that will be pushed to the top of execution stack(on the top) and once its completed it will be pop out.
2 stages are there for “execution context”:
->Creation Stage
Create the Scope Chain.
Create variables, functions and arguments.
Determine the value of “this”.
In creation stage or stage 1 , executioncontextobject is created. This is created before executing the function. in this stage, determain the variables,parameters, function declarations, variable declaration etc. This result is called “variableObject” .
In clarity, variables are created here with undefined value. Functions are created here, before the variables declaration.
->Activation/code Execution Stage
Assign values, references to functions and interpret / execute code.
Here code will be executed line by line.
(function(){
console.log(typeof a);
console.log(typeof fullname);
var a=”vinsha”;
var fullname=function(){
return “vinsha kp”;
};
}());
In the above example, we will get the value of “a” as undefined, because variables are created in stage 1 not assigning its value. We will get the value of “fullname” also has “undefined”. because it is also a variable in which a fucntion is assigned.
(function(){
console.log(typeof a);
console.log(typeof fullname);
var a=”vinsha”;
var fullname=function(){
return “vinsha kp”;
};
function a(){
return “fs”;
}
}());
In the above example, we will get the value of “a” as pointing to function a, because functions are created before varibales.Here before var a=”vinsha”; function a() created. So same name variable declaration is vomited.
we will get the value of “fullname” also has “undefined”. because it is also a variable in which a fucntion is assigned.
So variable and function declarations are hoisted to the top of their function scope. This is called Hoisting in javascript.
Reference and Tanks to : http://davidshariff.com/blog/what-is-the-execution-context-in-javascript/
Variable and function declarations are hoisted to the top of the function scope. In detail: The flow of execution of program is known as execution context. Global code –Initial section of program execution is known as global code. Function code – Once the execution enters into a function call. <script> var a=”Global execution”; // Global…
Variable and function declarations are hoisted to the top of the function scope. In detail: The flow of execution of program is known as execution context. Global code –Initial section of program execution is known as global code. Function code – Once the execution enters into a function call. <script> var a=”Global execution”; // Global…