9 Debugging Techniques Explained

Key Concepts

• Console Logging
• Using Breakpoints
• Error Stack Traces
• Conditional Breakpoints
• Watch Expressions
• Step-by-Step Execution
• Debugger Statements
• Error Handling with try/catch
• Using Source Maps

Console Logging

Console logging involves using the console.log() method to print values and messages to the browser's console. This technique helps in tracking the flow of execution and inspecting variable values at different stages.

Example:

let x = 10;
console.log('Value of x:', x);
x = x + 5;
console.log('Updated value of x:', x);
    

Analogies: Think of console logging as leaving breadcrumbs to trace your path.

Using Breakpoints

Breakpoints are points in the code where the execution pauses, allowing developers to inspect the current state of the application. Breakpoints can be set in the browser's developer tools or directly in the code editor.

Example:

function add(a, b) {
    let result = a + b; // Set breakpoint here
    return result;
}
console.log(add(2, 3));
    

Analogies: Breakpoints are like stopping points on a journey to check your map.

Error Stack Traces

Error stack traces provide a detailed report of the sequence of function calls that led to an error. They help in identifying the root cause of the error by showing the call stack at the time of the error.

Example:

function foo() {
    throw new Error('Something went wrong');
}
function bar() {
    foo();
}
bar();
    

Analogies: Stack traces are like a trail of footprints leading back to the source of a disturbance.

Conditional Breakpoints

Conditional breakpoints pause the execution only when a specific condition is met. This is useful for debugging scenarios where certain conditions are hard to reproduce.

Example:

for (let i = 0; i < 10; i++) {
    if (i === 5) { // Set conditional breakpoint here
        console.log('i is 5');
    }
}
    

Analogies: Conditional breakpoints are like setting traps to catch specific events.

Watch Expressions

Watch expressions allow developers to monitor the values of specific variables or expressions in real-time. They are useful for tracking changes in variables during debugging.

Example:

let a = 10;
let b = 20;
let sum = a + b;
console.log(sum);
    

Analogies: Watch expressions are like having a dashboard that displays key metrics.

Step-by-Step Execution

Step-by-step execution allows developers to execute code line by line, inspecting the state of the application at each step. This technique helps in understanding the flow of execution and identifying issues.

Example:

function multiply(a, b) {
    let result = a * b; // Step over this line
    return result;
}
console.log(multiply(2, 3));
    

Analogies: Step-by-step execution is like walking through a maze one step at a time.

Debugger Statements

The debugger statement pauses the execution of the code at the point where it is placed, allowing developers to inspect the current state. This is similar to setting a breakpoint.

Example:

function divide(a, b) {
    debugger; // Execution pauses here
    let result = a / b;
    return result;
}
console.log(divide(10, 2));
    

Analogies: Debugger statements are like setting up checkpoints in a race.

Error Handling with try/catch

Error handling with try/catch blocks allows developers to catch and handle exceptions gracefully. This technique helps in preventing the application from crashing and provides a way to log or display error messages.

Example:

try {
    let result = 10 / 0;
    console.log(result);
} catch (error) {
    console.error('Error:', error.message);
}
    

Analogies: Error handling with try/catch is like having a safety net to catch mistakes.

Using Source Maps

Source maps are files that map the compiled code back to the original source code. They are useful for debugging minified or transpiled code, allowing developers to see the original code in the browser's developer tools.

Example:

When using a build tool like Webpack, source maps can be generated to map the bundled code back to the original source files.

Analogies: Source maps are like a decoder ring that translates secret code back to readable text.