Does javascript assign by reference?

Is there any way I can be less verbose in JavaScript by pointing a local variable by to an objects property?

For instance in PHP I can do this:

$obj->subobject->property = 'Foo';
$property =& $obj->subobject->property;
$property =  'Bar';
echo $obj->subobject->property;
// output 'Bar'

It's not a very good example but you get the idea.

I want to copy this behaviour in Javascript. I'm quite often having to go quite deep into objects and it's getting quite annoying having to do:

if (please.stop.making.me[somevar].type.so.much.length) {
    please.stop.making.me[somevar].type.so.much[newSubObjectKey] = anObject;
}

// perform more operations on the object down here

It would be a lot easier to read and a lot easier to type:

var subObj = is.much.easier.to.type.once;
if (subObj.length) {
     subObj[newSubObjectKey] = anObject;
}

// now that's much better

I know I should really know this already, but I'm just advancing to "advanced novice" in JavaScript.

informatik01

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asked Jul 18, 2011 at 12:02

3

In JavaScript, everything is passed by value, but the variable's type will determine whether it's a reference passed by value or not;

• Objects are references
• Primitives (numbers, strings etc) are passed by value.

In simple terms, if you pass a variable to a function that's an array, modifying it in the function will affect the parent.

However, passing it a value in the array will not. Naturally, there's absolutely nothing stopping you wrapping a primitive in an object to ensure it works like a "pointer".

informatik01

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answered Jul 18, 2011 at 12:10

OliproOlipro

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2

You can assign a new variable to reference any depth in a chain of property keys, so long as the entry referred to isn't a primitive type.

This works because a bare object variable is actually a reference to that variable, so your new (shorter) variable can point to the same place.

However primitive number and string values are passed by value, so you can't create new references to those.

answered Jul 18, 2011 at 12:16

AlnitakAlnitak

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1

It would be a lot easier to read and a lot easier to type:

var subObj = is.much.easier.to.type.once;
if (subObj.length) {
     subObj[newSubObjectKey] = anObject;
}

Have you even tried the above? Because it works.

As for the actual question. You cannot have references or pointers to values. Everything is passed by value in javascript (not reference).

Edit: I forgot to mention some values are references. You still can't get a pointer to those reference values.

answered Jul 18, 2011 at 12:06

RaynosRaynos

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3

coffeeScript code

# result method
Object::r = (v) ->
    s=@
    st='global.'+v+'={'+'s'+'}'
    re=(eval st)
    str='global.'+v+'=re["s"]'
    eval(str)
    @


[1..10].r('a').
    map( (v) -> 'lorem_ipsum_'+v.toString() ).r('ar').
    join("__").r('s').
    split("__").reverse().r('arr')

console.log("\n")
console.log(a); console.log("\n")
console.log(ar); console.log("\n")
console.log(s); console.log("\n")
console.log(arr); console.log("\n")

screenShot

answered Feb 14, 2018 at 14:38

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