Does JavaScript pass by reference? [duplicate]

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Calling f2 results in printing out "a" value as 2 instead of 1, as the reference is passed and the "a" value in reference is updated.,JavaScript is pass by value.,For primitives, primitive's value is passed. For Objects, Object's reference "value" is passed.,Does JavaScript pass by references or pass by values?

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 copy of the reference held by the caller - i.e. the reference itself is passed by value:

function replace(ref) {
   ref = {}; // this code does _not_ affect the object passed
}

function update(ref) {
   ref.key = 'newvalue'; // this code _does_ affect the _contents_ of the object
}

var a = {
   key: 'value'
};
replace(a); // a still has its original value - it's unmodfied
update(a); // the _contents_ of 'a' are changed
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In Pass by value, parameters passed as an arguments create its own copy. So any changes made inside the function is made to the copied value not to the original value .,In Pass by reference, parameters passed as an arguments does not create its own copy, it refers to the original value so changes made inside function affect the original value. ,Pass by Value and Pass by Reference in Javascript,Pass By Value: In Pass by value, function is called by directly passing the value of the variable as an argument. So any changes made inside the function does not affect the original value.

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Introduction to javascript pass by reference and pass by value, Introduction to Functional Programming using Swift , The JavaScript for/of statement loops through the values of an iterable objects. It lets you loop over data structures that are iterable such as Arrays, Strings, Maps, etc...,Javascript pass by referencne


//javascript pass by reference
function callByReference(varObj) {

   console.log("Inside Call by Reference Method");

   varObj.a = 100;

   console.log(varObj);

}

let varObj = {
   a: 1
};

console.log("Before Call by Reference Method");

console.log(varObj);

callByReference(varObj)

console.log("After Call by Reference Method");

console.log(varObj);
}
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In JavaScript, we can divide data types into two different buckets, primitive data types and objects.,Understanding how primitive data types and objects behave in JavaScript,Let’s take a look at one more example that contain a variety of reference objects.,Finally, let’s take a look at how primitive data types and reference objects behave with equality operators.

Chart illustrating the primitive data types, or values, and the object types, or reference values

There are six primitive data types in JavaScript: string, number, boolean, undefined, null, and symbol as of ES6.

string
Chart illustrating the primitive data types, or values, and the object types, or reference values

There are six primitive data types in JavaScript: string, number, boolean, undefined, null, and symbol as of ES6.

number
Chart illustrating the primitive data types, or values, and the object types, or reference values

There are six primitive data types in JavaScript: string, number, boolean, undefined, null, and symbol as of ES6.

boolean
Chart illustrating the primitive data types, or values, and the object types, or reference values

There are six primitive data types in JavaScript: string, number, boolean, undefined, null, and symbol as of ES6.

undefined
Chart illustrating the primitive data types, or values, and the object types, or reference values

There are six primitive data types in JavaScript: string, number, boolean, undefined, null, and symbol as of ES6.

null
Chart illustrating the primitive data types, or values, and the object types, or reference values

There are six primitive data types in JavaScript: string, number, boolean, undefined, null, and symbol as of ES6.

symbol
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So in JS or Java, the references to variables can never be passed, rather variables can hold the value of a reference, and that value can get passed.,This also helps to further illustrate the difference between a value, and the variable that holds that value. In most illustrations, the two concepts are interchangeable. But of course, they're not the same thing.,the [...] examples illustrate that objects and scalar values are being handled very differently in memory once they're passed.,As you can see, the variable reference still contains the same object as it did before, at least by how javascript itself defines object identity. The variable still points to the same value, but the value itself was mutated.

// initialize our variables
let mostImportantNumber = 3.14;
let spanishNumbers = {
   one: 'uno',
   two: 'dos',
   three: 'tres'
};

// use these variables to initialize some NEW variables
let answerToEverything = mostImportantNumber;
let germanNumbers = spanishNumbers;

// mutate the NEW variables to our liking
answerToEverything = 42;
germanNumbers.one = 'einz';
germanNumbers.two = 'zwei';
germanNumbers.three = 'drei';

// inspect the ORIGINAL variables
console.log(mostImportantNumber);
// 3.14 - no surprise here
console.log(spanishNumbers);
// {one: 'einz', two: 'zwei', three: 'drei'}
// wait a minute... that doesn't look like Spanish
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In JavaScript, you can pass by value and by reference.,Passing by value means that every time you assign a value to a variable, a copy of that value is created. Every single time.,In JavaScript primitive types are passed around as values: meaning that each time a value is assigned, a copy of that value is created.,The simple rule of passing by value is that all primitive values in JavaScript are passed by value. Simple as that.

The primitives are numbers, booleans, strings, symbols, and special values null and undefined.

javascript // Primitivesconst number = 10;const bool = false;const str = 'Hello!';const missingObject = null;const nothing = undefined;
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In Pass by Reference, Function is called by directly passing the reference/address of the variable as the argument. Changing the argument inside the function affect the variable passed from outside the function. In Javascript objects and arrays follows pass by reference.,In Pass by Value, Function is called by directly passing the value of the variable as the argument. Changing the argument inside the function doesn’t affect the variable passed from outside the function.,However, when a variable refers to an object which includes array, the value is the reference to the object.,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.

Javascript always pass by value so changing the value of the variable never changes the underlying primitive (String or number).

function callByValue(varOne, varTwo) {
   console.log("Inside Call by Value Method");
   varOne = 100;
   varTwo = 200;
   console.log("varOne =" + varOne + "varTwo =" + varTwo);
}
let varOne = 10;
let varTwo = 20;
console.log("Before Call by Value Method");
console.log("varOne =" + varOne + "varTwo =" + varTwo);
callByValue(varOne, varTwo) console.log("After Call by Value Method");
console.log("varOne =" + varOne + "varTwo =" + varTwo);
output will be: -- -- -- -- -- -- -- - Before Call by Value Method varOne = 10 varTwo = 20 Inside Call by Value Method varOne = 100 varTwo = 200 After Call by Value Method varOne = 10 varTwo = 20
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Pass by value means that a copy of the actual parameter’s value is made in memory, i.e. the caller and callee have two independent variables with the same value. If the callee modifies the parameter value, the effect is not visible to the caller.,The values that are passed in the function call are called the actual parameters.,Callee does not have any access to the underlying element in the calling code.,Changes made to the passed variable do not affect the actual value.

void incrementCount(int count) //pass by value
{
   count = count + 1; //increments the value of count inside the function
}
int main() {
   int count = 0; // initialze the variable count
   int result = 0; //  initialze the variable result
   incrementCount(count); //call increment function
   cout << "Pass by value\n";
   cout << "Count:";
   cout << count; //prints the value of count after the function call
   return 0;
}

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