Expressions are the building blocks of programs. We can combine values with operators to compose an expression. An expression evaluates to some value.
Before you start this exercise, make sure you have watched the lecture first.
If you get stuck during this exercise, reference this walkthrough. Only watch enough of the walkthrough to get yourself unstuck, then pause the video and pick up the exercise on your own.
The fundamentals of any skill aren't particularly glamorous. We'll learn the "cool" stuff when you are ready. Crawl. Walk. Run.
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Create a new folder named expressions-exercise. Open it in VSCode. Create four files within this
folder: string-expressions.js, number-expressions.js, boolean-expressions.js,
comparisons.js.
After creating these files, your folder structure should look like this:
expressions-exercise/
├── string-expressions.js
├── number-expressions.js
├── boolean-expressions.js
└── comparisons.js
Make a mental prediction of what the following expressions will print:
console.log("river" + "town");
console.log("cat" + "dog");
console.log("New" + " York");
console.log("runner's knee" + "!");
console.log("man" + "bear" + "pig");To check your prediction, write the code into string-expressions.js and run it in your terminal
with node string-expressions.js. Don't copy and paste. Type everything manually. You should do
this line by line. This means you should type the first expression, run it. Add the second
expression, run it, and so on. Don't try to type all five lines and then run it all at once. You
will find it hard to pinpoint any typos if you do that.
Make predictions for what these number expressions evaluate to. Test your predictions by writing the
code to number-expressions.js and running it:
console.log(2 + 3);
console.log(10 - 15);
console.log(4 + 1 - 5);
console.log(4 * 3);
console.log(7 / 2);
console.log(4 + 2 * 3);
console.log((4 + 2) * 3);
console.log(5 % 2);
console.log(6 % 2);
console.log(7 % 2);
console.log(8 % 2);
console.log(19 % 8);
console.log(24 % 8);
console.log(7 % 4);
console.log(4 % 7);
console.log(5 + (10 % 5));
console.log((5 + 10) % 5);Make predictions for what these boolean expressions evaluate to. Test your predictions by writing
the code to boolean-expressions.js and running it:
console.log(false);
console.log(!true);
console.log(!false);
console.log(!!true);
console.log(false && false);
console.log(false && true);
console.log(true && false);
console.log(true && true);
console.log(false || false);
console.log(false || true);
console.log(true || false);
console.log(true || true);
console.log(!false || false);
console.log(false || (true && true));
console.log(false || !(true && true));
console.log(!true && (false || true));Make predictions for what these comparison expressions evaluate to. Test your predictions by writing
the code to comparisons.js and running it:
console.log(true === false);
console.log(false === false);
console.log(false !== true);
console.log(!true === false);
console.log(2 + 3 === 5);
console.log(4 < 0);
console.log(10 >= 10);
console.log(10.3 >= 10);
console.log(100 / 2 === 50);
console.log(100 % 2 === 0);
console.log(11 % 2 === 0);
console.log(7.0 === 7);
console.log(13 % 5 > 0);
console.log("potato" === "potato");
console.log("Tomato" === "tomato");
console.log("42" === 42);
console.log(5 > 3 && 1 === 0);