Javascript noob question - which one of the following is best practice and performance friendly, also welcome any other suggestions too. This is simplest version of original project. There will be 20+ variables and 10+ inner functions (Ex: 'process' in the case).
The advantage of Method 1 is it doesn't need to send arguments to the functions but as it nests all the functions inside the main function (possibly regenerate all the inner function for each instance of Foo). While the method 2 is free from function nesting but requires lot of arguments. Note that also there will be multiple instance of Foo constructor.
Method 1:
function Foo () {
var a = 1;
var b = 2;
var c = (a+b)/2;
var $element = $('#myElement');
var process = function (){
var x = a+b+c;
$element.css('left', x)
return x;
}
x = process ();
}
Method 2:
function Foo () {
var a = 1;
var b = 2;
var c = (a+b)/2;
var $element = $('#myElement');
x = process (a, b, c, $element);
}
function process (a, b, c, $element){
$element.css('left', x)
return x;
}
If you use the classical paradigm, you need to define classes but you don't need nested functions. Still, in scripting and classical, you MAY use nested functions if you want to. Only if you switch to the functional paradigm, which is the actual "native" paradigm of javascript, you NEED nested functions in some cases.
There are 3 ways of writing a function in JavaScript: Function Declaration. Function Expression. Arrow Function.
Note the difference between parameters and arguments: Function parameters are the names listed in the function's definition. Function arguments are the real values passed to the function. Parameters are initialized to the values of the arguments supplied.
A JavaScript function does not perform any checking on parameter values (arguments).
The separated functions are definitely the way to go for performance. While there are situations where the variable scoping of nested functions would be nice to have, the performance hit can be huge if the function is large.
Keep in mind that every time Foo if called, var process is reallocating all the memory for the new function that is being created, rather than keeping the function in memory and just passing it new parameters. If the function is big, this is going to be a pretty intense task for the Javascript interpreter.
Here are some hard numbers that may help as well (Contains performance comparisons and actual benchmarks that you can run in your own browser): http://jsperf.com/nested-functions-speed, http://jsperf.com/nested-named-functions/5
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