create a new array and push into it in one line - Javascript OOP

Question

I've this code with a function, wherein a I'm trying to define an array then on the next line pushing to it:

function Spot(value) {
  this.x = null;
  this.y = null;
  this.values = [];
  this.values.push(value);
}

I've tried this:

this.values = [].push(value);

and

this.values = (this.values || []).push(value);

But failed. Is there something wrong with the code.....

Answer 1

You are missing the array-initialisation syntax:

var x = [ 1, 2, 3 ];

in your case, this would be:

this.values = [ value ];

More info here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array

---

The code:

var x = ([]).push("y");

looks like it should generate an array and push the value to it. It does create the array, however the array is not returned to x, the new length of the array is returned, ie 1.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push

The push() method adds one or more elements to the end of an array and returns the new length of the array. [emphasis mine]

---

As noted in the comments, an alternative that is closer to your original attempt would be:

var x = ([]).concat("y");

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

Answer 2

Just take the value in an array.

function Spot(value) {
    this.x = null;
    this.y = null;
    this.values = [value];
}

var point = new Spot('foo')

console.log(point);