inserting a predefined object into a blank Javascript array

Question

If I enter the code line by line in a web console without the function() wrap (I use Chrome), it does what I want it to do, but I'm a bit stumped on why the code itself is returning 'undefined' as a block itself:

function () {

var x = [];

x[0] = {'first': 1, 'second': 2, 'third': 3};

return x;

}

I tried pushing the object with the x.push() function, but I don't think that really works either - many articles I've researched say I cannot use the .push() function with javascript objects. Basically I want the code to return:

[ {'first': 1, 'second': 2, 'third': 3} ]

Appreciate your help!

You've not given the function a name. How are you planning on calling the function? Note that you could also define the function as function makeMeAnArray() { return [ {'first': 1, 'second': 2, 'third': 3} ]; } — Heretic Monkey
– Heretic Monkey, Commented May 26, 2021 at 18:57
Does this answer your question? How to add an object to an array — Heretic Monkey
– Heretic Monkey, Commented May 26, 2021 at 19:00
Functions need to be called. If you just declare the function in the console (without syntax errors) then it will print undefined. But it's not clear what exactly you mean with "why the code itself is returning 'undefined' as a block itself". — Felix Kling
– Felix Kling, Commented May 26, 2021 at 19:13

Spectric · Accepted Answer · 2021-05-26 21:25:24Z

1

You need to name your function in order to call it (or use an IIFE). See the example below:

function doExample() {
  const obj = {
    'first': 1,
    'second': 2,
    'third': 3
  };
  const arr = [];

  arr.push(obj);

  return arr;
}


console.log(doExample());

Aside from not naming and calling calling the function, the code in your example looks like it should work fine - so you could use that as alternative to Array.prototype.push (demonstrated above).

edited May 26, 2021 at 21:25

Spectric

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answered May 26, 2021 at 18:58

Tom O.

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Comments

Bryan Dellinger · Accepted Answer · 2021-05-26 19:02:11Z

0

are you looking for an iife? immediately invoked function expression?

(function () {
var x = [];

x[0] = {'first': 1, 'second': 2, 'third': 3};
console.log(x);
return x;
})();

answered May 26, 2021 at 19:02

Bryan Dellinger

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