What is the difference between the two?

Question

I saw that the following JavaScript functions work in exactly the same way. Then what is the difference between them except the syntax . Function:

var functionName=function(){ //some code here }; function functionName(){ //some code here } 

I call them the same way as:

 functionName(); 

Please do not tell me that the syntax is different there, but there is some difference, for example

 1)speed of execution 2)Memory utilization etc. 

Thanks in advance!

Answer 1

This has been answered many times in StackOverflow. This is just a naming convention. Therefore, taking a few answers to the questions, I would say:

• Function declarations and variable declarations always move (“raised”) invisibly to the top of their area using a JavaScript interpreter. Functional parameters and language names obviously already exist.

• Advantages and disadvantages:

  There are several advantages of naming functions:

  • meta-analysis names. functionInstance.name will show you the name.
  • More importantly, the name will be printed in the stack trace.
  • names also help you write down self-documenting or literate code.

  There is one drawback of these function expressions

  • IE has memory leaks for NFE

• Another major difference

  The difference is that functionTwo is defined at parsing time for the script block, while functionOne is defined at runtime. For example:

   <script> // Error functionOne(); var functionOne = function() { } </script> <script> // No error functionTwo(); function functionTwo() { } </script> 

References

• var functionName = function () {} vs function functionName () {}
• Are functions or anonymous functions named in JavaScript?
• Named Functional Expressions Demystified
• Function declarations and function expressions .
• var functionName = function () {} vs function functionName () {}

Answer 2

• 1st — Named expressions of functions that must return a specific value to the caller.
• Part 2 is just a function, it depends on whether you return a value or not.