Declare multiple variables in JavaScript

Question

I want to declare multiple variables in a function:

function foo() {
    var src_arr     = new Array();
    var caption_arr = new Array();
    var fav_arr     =          


        

Answer 1

For all intents and purposes the literal [] notation syntax should be used. Since the Array constructor is ambiguous in how it deals with its parameters.

From the docs:

If the only argument passed to the Array constructor is an integer between 0 and 232-1 (inclusive), this returns a new JavaScript array with its length property set to that number. And that implies Array of passed length of empty slots with undefined values.

new Array(1, 2, 3); // Result: [1, 2, 3]
new Array(3); // Result: [empty × 3] with undefined at indexes
new Array('3') // Result: ['3']

//this was ambiguous
let x = new Array(5); // Result: [empty × 5]
x.push("Hello"); //expected x as ["Hello", empty, empty, empty, empty]
//Actual x: [empty × 5, "Hello"]

Destructuring syntax:

Another neater way to declare multiple variables is using destructuring assignment which enables unpacking values from arrays, or properties from objects, into distinct variables.

function foo() {
  //destructuring assignment syntax
  let [src_arr, caption_arr, fav_arr, hidden_arr] = [[], [], [], []];

  console.info("Variables::", fav_arr, hidden_arr, caption_arr, src_arr);

  fav_arr.push("fav");
  hidden_arr.push("hidden");

  //After adding some values to couple of arrays
  console.info("Variables::", fav_arr, hidden_arr, caption_arr, src_arr);
}

foo();