JavaScript keywords are reserved words that have special meanings and functions within the language. They form the foundation of JavaScript's syntax and structure, playing crucial roles in various aspects of programming.
JavaScript keywords can be categorized into several groups based on their functionality:
var, let, constif, else, switch, break, continue, returnfor, while, dofunctionclass, extends, supertry, catch, finally, throwJavaScript offers three keywords for variable declaration: var, let, and const. Each has its own scope and mutability characteristics.
var oldVariable = "I'm function-scoped";
let modernVariable = "I'm block-scoped";
const constantValue = "I can't be reassigned";
For more information on variable declaration, check out our guide on JavaScript Variables.
Control flow keywords help manage the execution path of your code. The if, else, and switch statements are fundamental for decision-making in JavaScript.
if (condition) {
// code to execute if condition is true
} else {
// code to execute if condition is false
}
switch (expression) {
case value1:
// code to execute
break;
case value2:
// code to execute
break;
default:
// code to execute if no case matches
}
Learn more about conditional statements in our JavaScript If-Else Statements and JavaScript Switch Statements guides.
Loop keywords allow you to repeat code blocks. The most common loop keywords are for and while.
for (let i = 0; i < 5; i++) {
console.log(i);
}
let j = 0;
while (j < 5) {
console.log(j);
j++;
}
Explore looping constructs further in our JavaScript For Loops and JavaScript While Loops guides.
const by default, and let when you need to reassign variables. Avoid var in modern JavaScript.break and continue in loops, as they can make code harder to follow.try...catch blocks for proper error handling in your code.this keyword behavior.Understanding JavaScript keywords is crucial for writing effective and efficient code. They provide the building blocks for creating complex programs and managing various aspects of your application's logic and structure.
As you continue your JavaScript journey, explore related concepts such as JavaScript Scope and JavaScript Function Declarations to deepen your understanding of how these keywords interact within your code.