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Which is is the best way to define a function in javascript . how to define a function using ':' like function_Name : function(){} .

user3392501
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  • You can't define a function like `function_Name : function(){}`. It needs to be `function function_Name(){}` or `var function_Name = function(){}` – Pugazh Sep 07 '16 at 10:14
  • You mean `var anyFunctionName = function(){}` and `function(){}` – Nikhil Ghuse Sep 07 '16 at 10:17
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    Check this answer - http://stackoverflow.com/questions/336859/javascript-function-declaration-syntax-var-fn-function-vs-function-fn and this http://davidbcalhoun.com/2011/different-ways-of-defining-functions-in-javascript-this-is-madness/ – Pugazh Sep 07 '16 at 10:18
  • Please take note that in standard international English questions are followed by a question mark (with no intervening space). Sentences start with a capital letter. Code in your question should be surrounded by backticks to make it formatted properly. You need to apply the same attention to detail in writing your question as I know you apply in your programming work. –  Sep 07 '16 at 11:38

2 Answers2

0

Hope this will be useful

Named function

function someName(){
 //rest of code
}

can be called by someName();

Function expression

var someName = function(){}

can be called by someName()

IIFE

(function(someParam){
 //rest of code
}(params))

IIFE can also can also written in this way

+function(someParam){
//rest of code
}(someParam)

Named function expression

var someVar = function someFoo(){};

this is called by someVar() . someFoo is only accessible inside itself

Arrow function(aka fat arrow)

var someVar= (param1, param2) => {return somereturn}

Function constructor

var adder = new Function('a', 'b', 'return a + b');

Beside this you can also take a look at call & apply

brk
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  • I think you left an extra `}` in your example of IIFE – GibboK Sep 07 '16 at 11:12
  • @GibboK thanks for pointing out the mistake. I have edited it – brk Sep 07 '16 at 11:31
  • Why would he look at `call` and `apply`? They are ways to invoke functions, not define them, which is what his question was about. –  Sep 07 '16 at 11:39
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There is no "best" way to define a function, it depends on your needs. For example if you have a function that validates something it makes sense to put it into a variable like Pugazh said:

var foo = function(){
  if (/*some condition*/) {
    //do something...;
    return true;
  }
  else {
    return false;
  }

And then use it like alert(foo()); and it will execute the function and return the value (true or false). Sometimes you want a named function you can call with options like:

function SaveData(data) {
    //Code to save something
}

And then call it like SaveData("Hello World");

And sometimes you just add a function without a name that is executed as a callback (e.g. in jquery) or when you perform a specific action but you define it at the event and not as a named function.

All types of functions have their use cases.

Broco
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