How Comma Operator Is Used Between The Statements?

The description of comma operator says You can use the comma operator when you want to include multiple expressions in a location that requires a single expression And the syntax

Solution 1:

It's only parsed as the comma operator when between expressions, not statements. let x = 3 is not an expression; it does not evaluate to any value. Trying to parse it as an expression does not work:

const result = let x = 3;
console.log(result);

The syntax let <variableName> = <expression>, <variableName2> = <expression2> is not invoking the comma operator - that syntax, when used around let, const, and var, simply initializes multiple variables at once, and said syntax simply happens to use commas, despite the fact that they're not interpreted as the comma operator.

In contrast, with

let x = 3,
    y = 5console.log(x,y)

You're not invoking the comma operator here, either: you have a parameter list. To invoke the comma operator, you also need to be not immediately inside a parameter list, eg:

let x = 3,
    y = 5console.log((x,y))

or

let x = 3,
    y = 5const someVar = (x,y);
console.log(someVar);

Solution 2:

The comma operator in JavaScript evaluates each of its operands. It returns the value of the last operand. Add multiple expressions using the comma operator.

The following is the syntax:

 expression1,expression2, ……expression

Yes, you can use the comma operator to add multiple parameters in a for loop:

for (var a = 0, b =5; a <= 5; a++, b--)

You can also use the comma operator in a return statement. Process before returning using comma:

function myFunc() {
  var a = 0;
  return (a += 1,a);
 }

Above you can see the value of a will process and then it will be returned Here is additional details: https://danhough.com/blog/single-var-pattern-rant/