Currently, I am diving into the world of JavaScript and expanding my knowledge. I recently stumbled upon a simple code snippet that uses '()();'. I couldn't find much information about it - what is this called? How is it used? Here is the code I found:
'use strict';
let obj, method;
obj = {
go: function() { alert(this); }
};
obj.go();
(obj.go)();
(method = obj.go)();
(obj.go || obj.stop)();
English is not my first language, so please excuse any mistakes.
When used independently, parentheses act as grouping operators in programming. Their purpose is to organize expressions and dictate the order of evaluation. For more information, you can visit this MDN page.
// Here's an illustration: // This represents the same concept
(obj.run)(); obj.run();
(method = obj.go)(); method = obj.go; method();
(obj.start || obj.end)(); // Triggering either start or end function after assigning it to a temporary variable
The code snippet illustrates the concept of how `this` is bound within a function execution context, specifically in the function `go`. It reaffirms that enclosing parentheses around a method does not change this behavior; `this` still refers to `obj`.
However, when parentheses are added around an expression involving operators, the scenario shifts. The resulting method is called without a specific `this` binding and defaults to `undefined`.
An alternate example is as follows:
(0,obj.go)();
In this case, the comma operator comes into play, signaling that we are dealing with an expression where `this` no longer points to `obj` during the method call.
Managing the sequence of operations is its main function. One could also opt to present the instructions in a clearer manner like so:
// (obj.go)();
obj.go();
// (method = obj.go)();
method = obj.go;
method();
// (obj.go || obj.stop)();
var method = obj.go || obj.stop;
method();
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