Quick Answer

Fix syntax errors: identify missing brackets, quotes, semicolons, and invalid JavaScript structure.

Understanding the Issue

The "SyntaxError: Unexpected token" occurs when the JavaScript parser encounters code that doesn't follow proper syntax rules. Common causes include missing or mismatched brackets, unclosed strings, missing commas in objects/arrays, or using reserved keywords incorrectly. These errors prevent code from running at all, as they are detected during the parsing phase. Understanding JavaScript syntax rules and using proper development tools helps identify and fix these errors quickly.

The Problem

This code demonstrates the issue:

Javascript Error 
// Problem 1: Missing brackets and braces
function myFunction() {
    if (true) {
        console.log("Hello");
    // Missing closing brace for function

const obj = {
    name: "Alice",
    age: 25
    // Missing closing brace for object

// Problem 2: Unclosed strings and missing commas
const message = "Hello world; // Missing closing quote
const users = [
    "Alice"
    "Bob"    // Missing comma between array elements
    "Charlie"
];

The Solution

Here's the corrected code:

Javascript Fixed 
// Solution 1: Proper bracket and brace matching
function myFunction() {
    if (true) {
        console.log("Hello");
    } // Properly closed if block
} // Properly closed function

const obj = {
    name: "Alice",
    age: 25
}; // Properly closed object

// Use consistent indentation to spot missing braces
function processData(data) {
    if (data) {
        for (let item of data) {
            if (item.valid) {
                console.log(item.name);
            }
        }
    }
} // All blocks properly closed

// Solution 2: Proper string and array syntax
const message = "Hello world"; // Properly closed string
const users = [
    "Alice",
    "Bob",      // Comma after each element
    "Charlie"   // No comma after last element (optional)
];

// Object syntax with proper commas
const userProfile = {
    name: "Alice",
    age: 25,
    email: "alice@example.com",
    active: true    // No comma after last property (optional)
};

// Template literal syntax
const greeting = `Hello, ${userProfile.name}!`;

// Proper function syntax variations
const regularFunction = function(param) {
    return param * 2;
};

const arrowFunction = (param) => {
    return param * 2;
};

const shortArrowFunction = param => param * 2;

// Proper array and object destructuring
const [first, second, third] = users;
const { name, age } = userProfile;

// Proper conditional and loop syntax
if (userProfile.active) {
    console.log("User is active");
} else {
    console.log("User is inactive");
}

for (let i = 0; i < users.length; i++) {
    console.log(users[i]);
}

// Common syntax error fixes
// Wrong: const x = ; (missing value)
const x = 0; // Correct

// Wrong: if (condition) then { } (invalid keyword)
if (true) { } // Correct

// Wrong: function() { } (missing name for function declaration)
function namedFunction() { } // Correct for declaration
const anonymousFunction = function() { }; // Correct for expression

Key Takeaways

Match all brackets and braces properly. Close all strings with matching quotes. Use commas correctly in arrays and objects. Use proper indentation to spot syntax issues visually.