My understanding is that this is actually very simple: Javascript is always pass by value, but when a variable refers to an object (including arrays), the “value” is a reference to the object. Changing the value of a variable never changes the underlying primitive or object, it just points the variable to a new primitive … Read more
Stop a Variable’s Reassignment While these answers are intellectually interesting, I’ve not read the short simple answer: Use the keyword final when you want the compiler to prevent a variable from being re-assigned to a different object. Whether the variable is a static variable, member variable, local variable, or argument/parameter variable, the effect is entirely … Read more
Primitives are passed by value, and Objects are passed by “copy of a reference”. Specifically, when you pass an object (or array) you are (invisibly) passing a reference to that object, and it is possible to modify the contents of that object, but if you attempt to overwrite the reference it will not affect the … Read more
First and foremost, the “pass by value vs. pass by reference” distinction as defined in the CS theory is now obsolete because the technique originally defined as “pass by reference” has since fallen out of favor and is seldom used now.1 Newer languages2 tend to use a different (but similar) pair of techniques to achieve … Read more
It’s interesting in JavaScript. Consider this example: function changeStuff(a, b, c) { a = a * 10; b.item = “changed”; c = {item: “changed”}; } var num = 10; var obj1 = {item: “unchanged”}; var obj2 = {item: “unchanged”}; changeStuff(num, obj1, obj2); console.log(num); console.log(obj1.item); console.log(obj2.item); This produces the output: 10 changed unchanged If obj1 was … Read more