How to Define an Array with Conditional Elements in JavaScript? Last Updated : 14 Aug, 2024 Comments Improve Suggest changes Like Article Like Report Sometime we may need to define an array with elements that depend on certain conditions. Such situation may occur when we have to dynamically generate arrays based on runtime logic such as including or excluding elements based on specific criteria. In this article, we'll explore various ways to define arrays with conditional elements in JavaScript.Following are the different approaches to defining an array with conditional elements in JavaScript:Table of ContentUsing the Ternary OperatorUsing Spread Operator with Conditional LogicUsing filter() MethodUsing the Ternary OperatorIn this approach, we are using the ternary operator which has a compact syntax that evaluates a condition and returns one of two values depending on whether the condition is true or false. When defining an array we use the ternary operator to include or exclude elements based on a condition. If the condition is true, value1 is included in the array otherwise value2 is included.Syntax:let array = [condition ? value1 : value2];Example: This example demonstrates using the ternary operator to include elements in an array based on a simple condition. JavaScript let isUserLoggedIn = true; let userRoles = ["guest", isUserLoggedIn ? "user" : "visitor"]; console.log(userRoles); Output[ 'guest', 'user' ] Using Spread Operator with Conditional LogicIn this approach we are using the spread operator (...). It expands an iterable (like an array) into individual elements. By combining it with conditional logic, we can spread elements into an array only when the condition is met.Syntax:let array = [value1, ...(condition ? [value2] : []), value3];Example: This example demonstrates using the spread operator to build an array conditionally. JavaScript let isAdmin = true; let features = [ "basic", ...isAdmin ? ["admin-panel"] : [], "User" ]; console.log(features); Output[ 'basic', 'admin-panel', 'User' ] Using filter() MethodFor more complex conditions we can use the filter() method it can be used to include elements based on a function's return value. This is particularly useful when dealing with arrays of objects or more intricate logic.Syntax:let array = values.filter(conditionFunction);Example: This example demonstrates how to use filter() to create a new array that only includes even numbers from the original array. JavaScript let numbers = [1, 2, 3, 4, 5, 6]; let evenNumbers = numbers.filter(num => num % 2 === 0); console.log(evenNumbers); Output[ 2, 4, 6 ] Comment More infoAdvertise with us Next Article How to Define an Array with Conditional Elements in JavaScript? yuvrajghule281 Follow Improve Article Tags : JavaScript Web Technologies Similar Reads How to create an array containing non-repeating elements in JavaScript ? In this article, we will learn how to create an array containing non-repeating elements in JavaScript.The following are the two approaches to generate an array containing n number of non-repeating random numbers.Table of ContentUsing do-while loop and includes() MethodUsing a set and checking its si 2 min read How to define custom Array methods in JavaScript? JavaScript arrays are versatile data structures used to store collections of items. When you want to iterate through the elements of an array, it's common to use loops like for, for...of, or forEach. 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