Tutorial on numbers. Doing bunch of Code Wars challenges where I had to verify if an argument is an number made me discover various ways it can be done. Below I will describe some of the things I used. typeof operator Basically we compare an argument to a value called 'number' . It will return for true decimals, negative numbers, math operations inside a parenthesis, infinity, NaN etc.. MDN documents going more in depth. typeof 10 === 'number'; typeof 10.2 === 'number'; typeof (5+10) === 'number'; Number.isInteger() We are passing a value inside the parenthesis and receive true or false depending if the valueis an integer. It will return false for decimals and math operations. MDN lists more cases. Number.isInteger(10) === true; Number.isInteger(10.2) === false; NaN There are a few ways this can be used: Number.isNaN(); method where we check if passed value is not a number. We can add ! sign...