Javascript object arrays - how to pass by value but keep name?

Question

I was coding in javascript and I needed to create an object with multiple sub-objects that would hold the same named variables. When I tried to push values to one sub-object, the others also would also get it. I simulated the behavior in the browser console as following:

object = {};
numbers = [0,1]; 
letters = ["a","b"]
fruits = ["peach", "pineapple"]


object.subObject1 = { numbers , letters , fruits };
object.subObject2 = { numbers , letters , fruits };

object.subObject1.numbers.push(3);
console.log(object.subObject2.numbers);

OUTPUT: [0, 1, 3]

So, when I push into the array1 sub-object. It also goes to the array2 sub-object, because apparently the numbers array is passed by reference. My question is, how can I do this so that they will keep the sub-object array property name ('numbers') but pass the array by value?

this(object.subObject1 = { numbers , letters , fruits }) is invliad it will not work in some browsers — Raghavendra
– Raghavendra, Commented Aug 14, 2015 at 5:18

Nathan · Accepted Answer · 2015-08-14 05:24:55Z

2

Try this code.

object.subObject1 = { numbers: numbers.slice(), letters: letters.slice(), fruits: fruits.slice() };
object.subObject2 = {  numbers: numbers.slice(), letters: letters.slice(), fruits: fruits.slice() };

object.subObject1.numbers.push(3);
console.log(object.subObject2.numbers);

slice apparently invokes that a new array is created for the objects based from the former array, not just passed as the reference.

edited Aug 14, 2015 at 5:24

answered Aug 14, 2015 at 5:17

Nathan

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2 Comments

Raghavendra Over a year ago

but declaration use this object.subObject1 = { numbers: numbers,.. }

sigmaxf Over a year ago

cool, that's excatly what I was missing, the "name: value" notation

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