Introduction
The question mark is a commonly used symbol in JavaScript, serving various purposes within the language. It can be used in conditional statements, as part of the ternary operator, and in regular expressions. In this article, we will explore the different uses of the question mark in JavaScript and how it affects the behavior of your code.
Conditional Statements
In JavaScript, the question mark is used as part of the conditional (ternary) operator. The conditional operator allows you to write shorter and more concise if-else statements. It has the following syntax:
condition ? expression1 : expression2
The condition is evaluated, and if it is true, expression1 is executed. If the condition is false, expression2 is executed. This operator is useful when you want to assign a value to a variable based on a condition. Here’s an example:
“`
let age = 20;
let message = (age >= 18) ? “You are an adult” : “You are a minor”;
console.log(message); // Output: “You are an adult”
“`
In this example, the condition `age >= 18` is evaluated. Since the age is 20, which is greater than or equal to 18, the expression `You are an adult` is assigned to the variable `message`.
Regular Expressions
The question mark also has a special meaning when used in regular expressions. It denotes an optional character or group. When placed after a character or a group, it means that the preceding element is optional, and the pattern can match with or without it. Here’s an example:
“`
let regex = /colou?r/;
console.log(regex.test(“color”)); // Output: true
console.log(regex.test(“colour”)); // Output: true
“`
In this example, the regular expression `/colou?r/` matches both “color” and “colour”. The question mark makes the “u” character optional, allowing the pattern to match with or without it.
Conclusion
The question mark in JavaScript serves multiple purposes. It is used in conditional statements as part of the ternary operator, allowing for shorter if-else statements. Additionally, it has a special meaning in regular expressions, denoting an optional character or group. Understanding these different uses of the question mark can help you write more concise and flexible code in JavaScript.
References
– developer.mozilla.org
– w3schools.com
