Number.
Converts a number into a string, also in a different numeral system, e.g. binary or hexadecimal.
- Returns
- A string with the number written in the chosen numeral system.
Example
#const points = 255
console.log(points.toString())
console.log(points.toString(2))
console.log(points.toString(16))
console.log(typeof points.toString())Definition and usage
#The toString() method returns the number written as text. Without an argument it uses the decimal system, so (42).toString() gives "42". String(42) and concatenating the number with a string give the same result, so in everyday code this method is mostly called with an argument.
The radix argument is the base of the numeral system, from 2 to 36. toString(2) shows the binary form, toString(16) the hexadecimal form, used among other things in CSS colors, and toString(36) uses digits plus every letter of the Latin alphabet, which gives short identifiers. The reverse conversion, from string to number, is done by Number.parseInt(text, radix).
When calling the method directly on an integer written as digits, wrap it in parentheses: (255).toString(16). Writing 255.toString(16) is a syntax error, because the period after the digits is treated as the start of a decimal part. On variables, parentheses aren’t needed.
Syntax
#number.toString()
number.toString(radix)Parameters
#radix
number 2-36, optional
The base of the numeral system. Defaults to 10.
More examples
#function toHex(r, g, b) {
return '#' + [r, g, b].map((part) => part.toString(16).padStart(2, '0')).join('')
}
console.log(toHex(250, 204, 21))
console.log(toHex(0, 128, 255))Without padStart(2, "0"), a zero would turn into a single "0" and the color would end up with too few digits.
const binary = (10).toString(2)
console.log(binary)
console.log(Number.parseInt(binary, 2))
console.log((123456789).toString(36))
console.log(Number.parseInt('21i3v9', 36))Browser support
#Widely available
Works in all modern browsers, phones included. You can use it without worry.
- Chrome
- Edge
- Firefox
- Safari
Good practices
#- For displaying numbers to users,
toLocaleString()andtoFixed()are better.toString()doesn’t add thousands separators or fix the number of decimal places. - On an integer written as digits, write
(10).toString(2). Without the parentheses you get a syntax error. - When converting to hexadecimal, pad the result with zeros using
padStart(2, "0"), otherwise 5 turns into "5" instead of "05".
Related entries
#- Number.parseInt()Converts the start of a string into an integer in a given numeral system.
- Number.prototype.toLocaleString()Formats a number the way a given language and region write it: thousands separators, decimal marks, currencies, and percentages.
- Number.prototype.toFixed()Converts a number into a string with a given number of decimal places.
- String.prototype.padStart()Pads a string on the left with the given text until it reaches the specified length. Perfect for leading zeros.
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