Adding an extra parenthesis into a method in JavaScript?

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Whenever I go through JavaScript code, I see a method that haves a pair of extra parentheses.

For example:

if( (typeOf VariableName) === "function" ) 

or

alert(("Hello World"))

What does these do, and why are they needed?

Function inside a round brackets - JavaScript, const add = (a, b) => a + b;. Just returning an object is that. However, curly brackets are also used by JS to denote the body of a function. So this� The constructor method is special, it is where you initialize properties, it is called automatically when a class is initiated, and it has to have the exact name "constructor", in fact, if you do not have a constructor method, JavaScript will add an invisible and empty constructor method.

Those particular examples would work the same without the extra parenthesis.

const x = () => {};

if( (typeof x) === "function" ) {
  console.log('yup');
}

if(typeof x === "function") {
  console.log('yup');
}

alert("Hello World")

Grouping operator ( ), Syntax. ( ). Description. The grouping operator consists of a pair of parentheses around an expression or sub-expression to override the� So I keep running into this problem where I will call a method without parenthesis because I figure it doesn’t have any parameters so it seems pointless to add parenthesis but i’ve learned that it won’t run if I dont do this. I dont understand it, but I know it must be done.

Do you remember [BODMAS] Rule,

Which has set of rules of arithmetic precedence for the way microprocessor do arithmetic decisions.

So highest precedence in Rule is bracket, We can set statements in bracket where end results might will affect because of Division Multipication Addition Subtraction [ DMAS ] precedences. (which in many cases are overlooked because of complexities of statements )

Arrow function expressions, To return an object literal expression requires parentheses around expression: Arrow Function var add = (a, b, c) => this.num + a + b + c; // call� In JavaScript, the functions wrapped with parenthesis are called “Immediately Invoked Function Expressions" or "Self Executing Functions. The purpose of wrapping is to namespace and control the visibility of member functions.

Chapter 15. Functions, You can call a function by mentioning its name, followed by arguments in parentheses: Method. You can store a function in a property of an object, which turns it into a of a function expression to the variable add and called it via that variable. More actual parameters than formal parameters: The extra parameters are� Methods can reference the object as this. The value of this is defined at run-time. When a function is declared, it may use this, but that this has no value until the function is called. A function can be copied between objects. When a function is called in the “method” syntax: object.method(), the value of this during the call is object.

Functions :: Eloquent JavaScript, Creating new words in prose is usually bad style. For example, this code defines square to refer to a function that produces the square of a The function body of a function created this way must always be wrapped in braces, even when it consists It ignores the extra arguments and computes the square of the first one. The slice() Method. slice() extracts a part of a string and returns the extracted part in a new string. The method takes 2 parameters: the start position, and the end position (end not included). This example slices out a portion of a string from position 7 to position 12 (13-1):

When you see a math problem containing parentheses, you need to use the order of operations to solve it. Take as an example the problem: 9 - 5 ÷ (8 - 3) x 2 + 6. In this problem, you would calculate the operation within the parentheses first, even if it is an operation that would normally come after the other operations in the problem.

Comments
  • The examples you gave would even work without extra (). Generally IIFE functions are enclosed inside ()
  • In the examples you posted they are not needed. Use if (typeof VariableName === 'function') and alert('Hello World')
  • for your first example, consider if( typeof (VariableName === "function")) this will resolve to if("boolean") and because "boolean" is a non falsy value this will always return true no matter what variableName is... sometimes you are not sure in what order the operators are applied, so you are explicit about it...
  • These extra parenthesis can be used for code clarity. (Not applicable in the examples you show, but perhaps there are some more complex order-of-operations that need clarified.)