If somebody uploads 82 songs, you need to work out how many playlists to create. For example, say you have a music site that includes playlists, and each playlist has ten songs on it. ceil ( E ) << 3īut when would you need to round a number up? A common usage is if you need to work out how many containers you need for something. ceil ( 2.5 ) // rounds up to 3 << 3 Math. ceil ( 2.3 ) // rounds up to 3 << 3 Math. Just provide the number you want to round up as an argument: Math. The method works in the same way as all the others. The name comes from ceiling and is the opposite of floor, implying the value is going up. Speaking of rounding up, this is exactly what Math.ceil does. Rounding down using Math.floor in the code above ensures that an index between 0 and 4 is returned, so every element in the array has an equal chance of being selected. The example below shows how a random element could be selected from an array using Math.floor: const fruit = const randomFruit = fruit << "□" Starting at zero is generally useful, as arrays in JavaScript are zero-indexed, so rounding down will make sure that the first element in the array could be selected. Rounding down ensures that the integer will start at zero and that each integer will have an equal chance of being returned. floor ( E ) << 2Ī common use of Math.floor is when creating random integers. floor ( 2.5 ) // rounds down to 2 << 2 Math. floor ( 2.921 ) // rounds down to 2 << 2 Math. floor ( 2.3 ) // rounds down to 2 << 2 Math. This always rounds a value down to the integer below (the name implies the number is being pushed down to the floor): Math. The next method we’ll look at is Math.floor. This might not result in a whole number, so you’d use Math.round() to round it to the closest value: const test1 = 86 const test2 = 93 const test3 = 95 const average = Math. For example, if you were calculating the average score over three tests, you’d add the three scores up and divide by three. Math.round() comes in handy if you want to round a number to the nearest integer value. round ( 2.5 ) // rounds up because it's exactly halfway << 3 Math. round ( 2.921 ) // rounds up because it's closer to 3 << 3 Math. round ( 2.3 ) // rounds down because it's closer to 2 << 2 Math. To use this method, we simply provide the number we want to round as the argument: Math. It uses this rule: if a number is exactly halfway between two integers, it will be rounded up. This is the most straightforward option, and simply rounds any number with a decimal part to the nearest integer. The first method we’ll look at is Math.round. Rounding Numbers in JavaScript with Math.round Now we have these constants defined, let’s take a look at some of the methods for rounding numbers in JavaScript. Pro tip: you can also make this assignment in a single line using object destructuring: const = Math Both of these values are properties of the Math object, but let’s assign them to some variables to make them easier to deal with: const PI = Math. In our examples, we’ll use two of the most important mathematical constants to demonstrate different types of rounding: Pi, which is the ratio of the circumference of a circle to its diameter, and e, which is the base of natural logarithms and also known as “Euler’s number”. Thankfully, JavaScript’s Math object provides a number of ways to round numbers to an integer value. When dealing with numerical values, we can sometimes perform calculations that end up with fractional parts that need rounding to a whole number - such as when you’re working out an average price, or dealing with random numbers.
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