In JavaScript, you can pass by value and by reference. Show The main difference between the two is that passing by value happens when assigning primitives while passing by reference when assigning objects. Let's discuss values and references in more detail in this post. 1. Understanding primitive and objectsJavaScript provides 2 categories of data types: primitives and objects. The primitives are numbers, booleans, strings, symbols, and special values
The second category is objects. Particularly the plain object, arrays, functions, and more — are all objects.
Saying it differently, anything that is not a primitive value is an object. 2. ValuesThe simple rule of passing by value is that all primitive values in JavaScript are passed by value. Simple as that. Passing by value means that every time you assign a value to a variable, a copy of that value is created. Every single time.
Let me show you how pass by value manifests itself. Let's say you have 2 variables
The first statement The second statement Later, 3. ReferencesThe pass by reference, however, manifests itself differently. When creating an object you're given a reference to that object. If 2 variables hold the same reference, then changing the object reflects in both variables.
Let's check the following code sample:
The first statement Then
Note: for simplicity, I say that variables hold references to objects. But strictly saying variables in JavaScript hold values that are references to objects. 4. Comparing values and comparing referencesUnderstanding the difference between values and references is important when you want to compare objects. When using the strict comparison operator
But the comparison operator
The comparison operator returns 5. SummaryIn JavaScript primitive types are passed around as values: meaning that each time a value is assigned, a copy of that value is created. On the other side objects (including plain objects, array, functions, class instances) are references. If you modify the object, then all variables that reference that object are going to see the change. The comparison operator distinguishes comparing values and references. 2 variables holding references are equal only if they reference exactly the same object, but 2 variables holding values are equal if they simply have 2 same values no matter where the value originates: from a variable, literal, etc. Often, however, you might want to compare objects by their structure rather than by reference. Check out the post How to Compare Objects in JavaScript. Is JavaScript call by reference or value?JavaScript is always pass-by-value. This means everything in JavaScript is a value type and function arguments are always passed by value.
Does JavaScript assign by reference?The Bottom Line on JavaScript References
On variable assignment, the scalar primitive values (Number, String, Boolean, undefined, null, Symbol) are assigned-by-value and compound values are assigned-by-reference. The references in JavaScript only point at contained values and NOT at other variables, or references.
Are JavaScript objects passed by reference?In Javascript objects and arrays follows pass by reference. so if we are passing object or array as an argument to the method, then there is a possibility that value of the object can change.
Are JavaScript arrays passed by reference?In Javascript objects and arrays are passed by reference.
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