How to Conditionally Add a Property or Member to an Object in JavaScript?

How to Run or Call Executable (EXE) From JavaScript?

In JavaScript, we add properties or members to objects dynamically to make your code concise and readable. You should read this article if you don’t know how to add a member to an object conditionally. Keep reading. 🔎

In JavaScript, objects are a fundamental data structure that allows developers to store and manipulate data as key-value pairs. Objects can be used to represent complex data structures and provide a way to organize related data together. One of the most common tasks when working with objects in JavaScript is to conditionally add a member to an object based on specific criteria.

We can add a member to an object by using different techniques such as the ternary operator, if statement, spread operator, Object.assign(), and logical And operator. Using these techniques, you can write concise and readable code in JavaScript. Before we solve the mystery of how to add members conditionally, we first have to understand the concept of objects and members in JavaScript. 

So without any further delay, dive deep into the article.

 

 

What Are Objects and Members in JavaScript?

An object is a group of related data and functions represented in JavaScript as key-value pairs. Both properties and methods can be found in an object. A property is a value attached to an object, whereas a method is a function that may be used on an object to carry out an operation or return a result.

An object in JavaScript is defined using curly braces {} and can contain zero or more properties, each of which is a key-value pair separated by a colon :. A string used to identify a property is used as the key. At the same time, the value can be any valid JavaScript expression, including other objects, arrays, functions, and primitive data types (such as strings, numbers, and booleans). 

Let’s use a straightforward example to clarify this idea:

 

Code

// Example of Object and Member

// employ object has four members

let employ = {

  id:20,

  name:'Zeshan',

  age:25,

  welcome:function(){

    alert('Welcome Mr '+ this.name)

  }

}

// call function

employ.welcome();

//Print value of employ on-screen

console.log(employ);

 

Output

Welcome Mr Zeshan

{ id: 20, name: 'Zeshan', age: 25, welcome: [Function: welcome] }

 

 

Different Ways to Conditionally Add a Property or Member to an Object in JavaScript

JavaScript has several ways to add a member to an object conditionally. Here are some of them:

  1. Using the ternary operator.
  2. Using the if statement.
  3. Using the logical And operator.
  4. Using the Object.assign() method.
  5. Using the spread operator.

 

Method 1: Using the Ternary Operator

The ternary operator is just like an if-else statement in JavaScript. It is often used to assign a value to a variable based on a condition. In some cases, the ternary operator can make code more concise and easier to read, especially when the if-else statement is simple and only has two possible outcomes. 

We can use the ternary operator to add a member to an object conditionally. We can understand how its works with the help of a simple example:

 

Code

// Example of Ternary operator

// employ object has four members

let employ = {

  id:20,

  name:'Zeshan',

  age:25,

  salary:25000,

    

}

//Print value of employ before addition

console.log("employ object:",employ);

// Check salary; if it is more than 20000, then 

// set role member to manager otherwise undefined

employ.role = employ.salary>20000 ? 'Manager': undefined;

console.log("employ object after addition:", employ);

 

Output

employ Object: { id: 20, name: 'Zeshan', age: 25, salary: 25000 }

employ Object after addition: { id: 20, name: 'Zeshan', age: 25, salary: 25000, role: 'Manager' }

 

 

Method 2: Using the If Statement

In JavaScript, the if statement is a control flow statement that allows you to execute a code block if a specified condition is true. The general syntax of the if statement is as follows:

 

Syntax

if (condition) {

  // Associated Code

}

 

Optionally, you can add an else block to the if statement, which will be executed if the condition is false. The general syntax for an if-else statement is as follows:

 

Syntax

if (condition) {

  // Associated Code

} else {

  // Associated Code

}

 

We can use an if statement to add a member to an object conditionally. Let’s understand its works with the help of this simple example:

 

Code

//example of if statement

// employ object has four members

let employ = {

  id:20,

  name:'Zeshan',

  age:25,

  salary:5000,    

}




//Print value of employ before addition

console.log("employ object:",employ);




// Check salary; if it is more than 20000, then 

// set role member to manager otherwise undefined

if(employ.salary>20000)

employ.role ='Manager'

else

employ.role =undefined;

console.log("employ object after addition:", employ);

 

Output

employ Object: { id: 20, name: 'Zeshan', age: 25, salary: 5000 }

employ Object after addition: { id: 20, name: 'Zeshan', age: 25, salary: 5000, role: undefined }

 

 

Method 3: Using the Logical And Operator

The logical And operator (&&) is a binary operator in JavaScript that returns true if both operands are true and otherwise false. We can use JavaScript’s logical And (&&) operator to add a member to an object conditionally.

 

The general syntax for this technique is:

obj.propertyName && (obj.newProperty = Value);

 

Here, obj is the name of the Object you want to add a property to, propertyName is the name of a property that already exists on the Object, and value is the value you want to assign to the newProperty.

The logical And operator checks whether the value of propertyName is true. If it is, the expression on the operator’s right-hand side is evaluated. This expression assigns a new property newProperty, to the obj Object, with the value Value.

If the value of propertyName is false, the logical And operator short-circuits and returns false without evaluating the expression on the right-hand side. This ensures that the new property is added only if the existing property is true.

Let’s understand it with the help of a simple example:

 

Code

// Example of And operator

// student object has four members

const student = {

  Id: 20,

  name: 'Afridi',

  marks: 70,

};

// we can use && operator to add member conditionally

// if marks are more than 40, add status member

student.marks>40 && (student.status = 'pass');

console.log(student);

 

Output

{ Id: 20, name: 'Afridi', marks: 70, status: 'pass' }

 

 

Method 4: Using the Object.assign() Method

In JavaScript, Object.assign() is a built-in method that allows you to copy the values of all enumerable properties from one or more source objects to a target object. The syntax for Object.assign() is as follows:

 

Syntax

Object.assign(target_obj, source_obj);

 

We can also use the Object.assign method to add a member to an object conditionally.  Let’s understand the working of Object.assign() with the help of a simple example:

 

Code

// Example of Object.assign() method

// employ object has four members

let employ = {

  id:20,

  name:'Zeshan',

  age:25,

  salary:5000,

}

//Print value of employ before addition

console.log("employ object:",employ);

// Check salary; if it is more than 20000, then 

// set role member to manager; otherwise not a manager

Object.assign(employ, employ.salary>20000 ? { role: 'manager' } : {role:'not manager'});

console.log("employ object after addition:", employ);

 

Output

employ Object: { id: 20, name: 'Zeshan', age: 25, salary: 5000 }

employ Object after addition: { id: 20, name: 'Zeshan', age: 25, salary: 5000, role: 'not manager' }

 

 

Method 5: Using the Spread Operator

In JavaScript, the spread operator (…) is an operator that allows you to expand an iterable object, such as an array or a string, into individual elements. The spread operator can be used in various ways, including passing arguments to functions, merging arrays or objects, and creating copies of arrays or objects.

JavaScript’s spread operator can be combined with the ternary operator to conditionally add a member to an object. Here’s an example to understand the working of a spread operator:

 

Code

// Example of the spread operator

// student object has four members

const student = {

  Id: 20,

  name: 'Afridi',

  marks: 70,

  // add member status based on the condition

  ...(this.marks > 40 ? { status: 'Pass' } : {status: 'fail'})

};

console.log(student);

 

Output

{ Id: 20, name: 'Afridi', marks: 70, status: 'fail' }

 

 

Conclusion

In JavaScript, you can conditionally add a member to an object using the ternary operator, spread operator, Object.assign(), if statement, or logical And operator. These techniques allow you to add a new property to an object based on some condition or set of conditions. Using these methods, you can write concise and readable code and add properties to objects dynamically.

The ternary operator can conditionally add a property to an object and is a concise way to create an if-else statement. The spread operator can copy an existing object and add new properties simultaneously, using object literal syntax. The logical And operator can conditionally add a property to an object based on whether an existing property is true.

These techniques can be helpful when you need to dynamically add a property to an object based on some condition that may or may not be met at runtime. 

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