parseInt(str, base) parses the string str into an integer in numeral system with given base, 2 ≤ base ≤ 36.Can write numbers directly in hex ( 0x), octal ( 0o) and binary ( 0b) systems.A negative number after "e" causes the number to be divided by 1 with given zeroes.Append "e" with the zeroes count to the number.There are more functions and constants in Math object, including trigonometry, which you can find in the docs for the Math object. These rounding rules normally don’t allow us to see that “tiny precision loss”, but it exists.Īlert( Math.pow(2, 10) ) // 2 in power 10 = 1024 The numeric format IEEE-754 solves this by rounding to the nearest possible number. There’s just no way to store exactly 0.1 or exactly 0.2 using the binary system, just like there is no way to store one-third as a decimal fraction. For the same reason, in the binary numeral system, the division by powers of 2 is guaranteed to work, but 1/10 becomes an endless binary fraction. So, division by powers 10 is guaranteed to work well in the decimal system, but division by 3 is not. It becomes an endless fraction 0.33333(3). In decimal numeral system such numbers are easily representable. What is 0.1? It is one divided by ten 1/10, one-tenth. But fractions like 0.1, 0.2 that look simple in the decimal numeric system are actually unending fractions in their binary form. That would surprise anyone.Ī number is stored in memory in its binary form, a sequence of bits – ones and zeroes. Ouch! Imagine you’re making an e-shopping site and the visitor puts $0.10 and $0.20 goods into their cart. But what if we’d like to round the number to n-th digit after the decimal?įor instance, we have 1.2345 and want to round it to 2 digits, getting only 1.23.įor example, to round the number to the 2nd digit after the decimal, we can multiply the number by 100, call the rounding function and then divide it back.Īlert( 0.1 + 0.2 ) // 0.30000000000000004 These functions cover all of the possible ways to deal with the decimal part of a number. Here’s the table to summarize the differences between them: unc (not supported by Internet Explorer) Removes anything after the decimal point without rounding: 3.1 becomes 3, -1.1 becomes -1. Math.round Rounds to the nearest integer: 3.1 becomes 3, 3.6 becomes 4, the middle case: 3.5 rounds up to 4 too. Math.ceil Rounds up: 3.1 becomes 4, and -1.1 becomes -1. There are several built-in functions for rounding: Math.floor Rounds down: 3.1 becomes 3, and -1.1 becomes -2. One of the most used operations when working with numbers is rounding. And if we place one more dot, then JavaScript knows that the decimal part is empty and now goes the method.Īlso could write (123456).toString(36). If we placed a single dot: 123456.toString(36), then there would be an error, because JavaScript syntax implies the decimal part after the first dot. If we want to call a method directly on a number, like toString in the example above, then we need to place two dots. Please note that two dots in 123456.toString(36) is not a typo.
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