Numbers

To write numbers with many zeroes:

• Append "e" with the zeroes count to the number. Like: 123e6 is the same as 123 with 6 zeroes 123000000.
• A negative number after "e" causes the number to be divided by 1 with given zeroes. E.g. 123e-6 means 0.000123 (123 millionths).

For different numeral systems:

• Can write numbers directly in hex (0x), octal (0o) and binary (0b) systems.
• parseInt(str, base) parses the string str into an integer in numeral system with given base, 2 ≤ base ≤ 36.
• num.toString(base) converts a number to a string in the numeral system with the given base.

For regular number tests:

• isNaN(value) converts its argument to a number and then tests it for being NaN
• Number.isNaN(value) checks whether its argument belongs to the number type, and if so, tests it for being NaN
• isFinite(value) converts its argument to a number and then tests it for not being NaN/Infinity/-Infinity
• Number.isFinite(value) checks whether its argument belongs to the number type, and if so, tests it for not being NaN/Infinity/-Infinity

For converting values like 12pt and 100px to a number:

• Use parseInt/parseFloat for the “soft” conversion, which reads a number from a string and then returns the value they could read before the error.

For fractions:

• Round using Math.floor, Math.ceil, Math.trunc, Math.round or num.toFixed(precision).
• Make sure to remember there’s a loss of precision when working with fractions.