Debugging

Beyond console.log(), every browser's developer tools include a real debugger — set a breakpoint by clicking a line number in the "Sources" tab, or add the debugger; statement directly in code:

function calculateTotal(prices) {
    debugger; // execution pauses here when devtools are open
    return prices.reduce((sum, p) => sum + p, 0);
}

While paused, you can inspect every variable currently in scope, and step through the code one line at a time.