Are values passed by reference or by value in JavaScript?
The answer is: it depends!
Primitive types are passed by value.
Objects are passed by reference.
Primitive types are numbers, strings, booleans, null, undefined and symbols.
Everything that’s not a primitive type is an object. Arrays are objects. Functions are objects.
When you pass a number to a function, it’s copied into the function:
const increment = num => {
num = num + 1
}
const num = 2
increment(num)
console.log(num) //2If you pass an object, it’s passed by reference, so if you modify one of its properties, also the original object is modified:
const increment = num => {
num.value = num.value + 1
}
const num = {
value: 2
}
increment(num)
console.log(num.value) //3download all my books for free
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