Exceeding String Bounds in TypeScript

When accessing string characters with indices, the most common problem we can run into is exceeding the string's bounds.

Remember, the characters of a string are normally indexed from 0 to length - 1.

Any index which is strictly greater than length - 1 is invalid.

When you try to access a character with an invalid index, TypeScript returns undefined:

let car = "ford";

// Valid indices: 0, 1, 2, 3
console.log(car[0]); // Output: f
console.log(car[3]); // Output: d

// Invalid indices: 4, 30
console.log(car[4]); // Output: undefined
console.log(car[30]); // Output: undefined

Some languages like Python wouldn't even let this code run, but throw an IndexError. TypeScript is more permissive, which is not necessarily a good thing.

As a programmer, I'd rather be told when I made a mistake early on so I can fix it, instead of running into problems later on and not knowing what the root of those problems is.

In conclusion, we always want to double check our code to make sure that we don't exceed one string's bounds in our programs.

Assignment
Follow the Coding Tutorial and let's practice with string bounds!

Hint
Look at the examples above if you get stuck.