Debugging

Identify various kinds of errors + Case Study.

1. Python Tutor

Write a program to find the smallest value in an array.

Use http://pythontutor.com/ to visualize your code.

2. Common Errors - Run the following code snippets and observe errors.

(If you are using a language other than JavaScript, try to recreate the same errors in your language)

ReferenceError: variable is not defined

let arr = [1, 2, 3]
ar.push(4);

TypeError: Cannot read property 'x' of undefined

function doubleArrayElements(arr) {
    let b = [];
    for (let a of arr) {
        b.push(a * 2);
    }
    return b;
}

Silent errors - mostly due to type coersion

Adding string to number

let x = 1;
let y = "2"
console.log(x + y);

Adding a number to an array

let arr = [1, 2, 3, 4];
let y = 5
z = arr + y;
console.log(z)

Dividing by 0

console.log(1 / 0);

Parse Int - NaN

let word = "hello"
let number = parseInt(word);
function square(n) {
    return n * n;
}
console.log(square(number));