Pass a variable in an array, not a value in javascript

Question

is there a way to pass a variable itself, not a value in javascript? I remember being able to do so in flas as3 if i remember correct which was based on javascript. I'm not sure why i can't do the same here. Your help would be much appreciated.

variable1: false,

function1() {

    this.variable1 = true //this works of course console.log(this.variable1) prints true
}

function2() {

    var temparray1 = [this.variable1]
    temparray1[0] = true //does not work like i want, it's the value in the array that change, not this.variable1

    console.log(this.variable1) //prints still false
    console.log(temparray1[0]) //prints true
}

This is not how the language is supposed to work, and this would be extremely confusing to any JavaScript developer who has to use your code later. — sbking, Aug 02 '17 at 16:56
Possible duplicate of [Javascript by reference vs. by value](https://stackoverflow.com/questions/6605640/javascript-by-reference-vs-by-value) — Nisarg Shah, Aug 02 '17 at 16:57
https://stackoverflow.com/questions/6605640/javascript-by-reference-vs-by-value — kyle, Aug 02 '17 at 17:01
Ok so how to achieve this dynamically. Let's say you have a table and for when you match an item in a array, you want to change the variable you chose at that index. — The Architect, Aug 02 '17 at 23:48

score 2 · Answer 1 · answered Aug 02 '17 at 16:55

Primitive datatypes are always passed as value, never as a reference. Javascript passes objects as references though, so you can create an object and assign the value to an attribute like so:

variable1 = {yourValue : false}
...
var temparray1 = [this.variable1]
temparray1[0].yourValue = true;

Now when accessing variable1.yourValue it should be true.

score 0 · Answer 2 · answered Aug 02 '17 at 16:55

There is no way to pass a boolean by reference in Javascript, but as a workaround you can wrap your boolean in an object, like this:

var variable1 = { value: false }

function setVar() {
    variable1.value = true
}

function test() {
    var temparray1 = [variable1]
    temparray1[0].value = true
    console.log(variable1.value) // prints true
    console.log(temparray1[0].value) // also prints true
}

score 0 · Accepted Answer · answered Aug 02 '17 at 17:03

Javascript always passes by value. So in your case

var temparray1 = [this.variable1]

becomes

var temparray1 = [false]

So changing it does not change variable1. But if you want to change variable1 by changing the array, you should either have variable1 as an array or object. For Example:

this.variable1 = {
    value: false
}

var temparray1 = [this.variable1];
temparray1[0].value = true;

Here also, Javascript passes by value, but now this.variable1 is a reference to the object and temparray1[0] has the value of variable1, So it is also a reference to the same object.So we are changing that object.

Thank you for your input. Also how can i fix this post so as to unlock my account, i cannot post and i don't know what is wrong. Or how to improve this question. Thanks. — The Architect, Jul 28 '18 at 05:43

Pass a variable in an array, not a value in javascript

3 Answers3