14.
Which of the following is a valid JavaScript syntax?
var firstName = "John";
const 1stName = "Jane";
let first__name = "Alex";
int lastName = "Smith";
Correct: A, C
In JavaScript, variable names can start with a letter, underscore, or a dollar sign. They can contain letters, numbers, underscores, or dollar signs. A1 is a valid syntax as it declares a variable "firstName" using the "var" keyword and assigns it the value "John". A3 is also valid as it declares a variable "first__name" using the "let" keyword and assigns it the value "Alex". A2 is not valid as it starts with a number, which is not allowed. And A4 is not valid because JavaScript does not have a separate data type called "int".