Chinese reader may go to Chinese Version.
A golang fmt.Printf implementation in Node.js.
Please refer to http://golang.org/pkg/fmt/ for the full specification.
npm install gofmt --save
var sprintf = require('gofmt')()
console.log(sprintf("Hello, %s", "world!")) // Hello, world!
console.log(sprintf("%4.2f%%", 72.426)) // 72.43% %% -> %
% #-0 4 . 2 f
flags width presision verbs
+ always print a sign for numeric values;
guarantee ASCII-only output for %q (%+q)
- pad with spaces on the right rather than the left (left-justify the field)
# alternate format: add leading 0 for octal (%#o), 0x for hex (%#x);
0X for hex (%#X); suppress 0x for %p (%#p);
for %q, print a raw (backquoted) string if strconv.CanBackquote
returns true;
write e.g. U+0078 'x' if the character is printable for %U (%#U).
' ' (space) leave a space for elided sign in numbers (% d);
put spaces between bytes printing strings or slices in hex (% x, % X)
0 pad with leading zeros rather than spaces;
for numbers, this moves the padding after the sign
Width is specified by an optional decimal number immediately following the verb. If absent, the width is whatever is necessary to represent the value.
Precision is specified after the (optional) width by a period followed by a decimal number. If no period is present, a default precision is used (depending on different verbs). A period with no following number specifies a precision of zero. Examples:
%f: default width, default precision
%9f width 9, default precision
%.2f default width, precision 2
%9.2f width 9, precision 2
%9.f width 9, precision 0
%s, %f and %% that presented in above example we call it verbs.
verbs%v: same as %s
%T: output the type name of current operand
%%：output `%`，it does not consume operand
var sprintf = require('gofmt')()
console.log(sprintf("%T", 1)) // number
console.log(sprintf("%T", {})) // object
console.log(sprintf("%T", new Error())) // error
console.log(sprintf("%T", new RegExp())) // regexp
console.log(sprintf("%T", Array(1))) // array
console.log(sprintf("%T", null)) // null
console.log(sprintf("%T", undefined)) // undefined
%t outputs the boolean result of the operand.
console.log(sprintf("%t", true)) // true
console.log(sprintf("%t", 1)) // true
console.log(sprintf("%t", 0)) // false
console.log(sprintf("%t", '')) // false
console.log(sprintf("%t", new Array())) // false
For integer, output its base 2 representation. For floating-point output its decimalless scientific notation with exponent a power of two.
console.log(sprintf("%b", 1024)) // 10000000000
console.log(sprintf("%b", 1.1)) // 4953959590107546p-52
console.log(sprintf("%b", -0.3)) // -5404319552844595p-54
Output the character represented by the corresponding Unicode code point.
console.log(sprintf("%cBCD", 65)) // ABCD
console.log(sprintf("%c国", 20013)) // 中国
The floating-point will be truncated but not round.
console.log(sprintf("%d", 1.5)) // 1
console.log(sprintf("%+d", 1.5)) // +1 flag '+', force to output the sign
console.log(sprintf("% d", 1.5)) // ' 1' flag ' ', leave a placeholder for positive sign
console.log(sprintf("%4d", 1.5)) // ' 1' minimum width is 4
// align to right by default
// pad the remaining spaces with ' ' on the left
console.log(sprintf("%04d", 1.5)) // 0001 flag '0'
// pad the remaining spaces with '0' on the left
console.log(sprintf("%-4d", 1.5)) // '1 ' flag '-'
// align to the left and always pad with ' '
console.log(sprintf("%o", 1)) // 1
console.log(sprintf("%.3o", 1)) // 001 pad to 3 digits with '0'
console.log(sprintf("%#o", 1)) // 01 flag '#'
// Add a prefix '0' to the output if the first character isn't '0'.
For integer, the output is a single-quoted string safely escaped with the literal expression of non-printable character.
For string, the output is a double-quoted string safely escaped with the literal expression of non-printable characters.
console.log(sprintf("%q", 65)) // 'A'
console.log(sprintf("%q", 7)) // '\t' ASCII 7 has been converted to '\t'
console.log(sprintf("%q", 0x038b)) // '\u038b' '\u038b' are also non-printable
console.log(sprintf("%q", "\u038b\tabc")) // "\u038b\tabc"
console.log(sprintf("%#q", "\tabc")) // ' abc' No escape, but using single-quotes instead of double-quotes
%x: with lower-case letters for a-f, e.g. 0x0a.
%X: with upper-case letters for A-F, e.g. 0X0A.
Operand is a number:
console.log(sprintf("%x", 65536)) // 10000
console.log(sprintf("%.4x", 255)) // 00ff
console.log(sprintf("%#.4x", 255)) // 0x00ff flag '#' add '0x' as prefix
console.log(sprintf("%#.4x", -255)) // -0x00ff
console.log(sprintf("%#.4X", -255)) // -0X00FF
Operand is a string:
console.log(sprintf("%x", "abc")) // 616263
console.log(sprintf("%#x", "abc")) // 0x616263
console.log(sprintf("% x", "abc")) // 61 62 63, flag ' ' separate each characters
console.log(sprintf("% #x", "abc")) // 0x61 0x62 0x63
console.log(sprintf("% #x", "中文ABC")) // 0x4e2d 0x6587 0x41 0x42 0x43
console.log(sprintf("%U", 65)) // U+0041
console.log(sprintf("%#U", 65)) // U+0041 'A', flag '#'
// Both the unicode format and its corresponding character will be outputted
console.log(sprintf("%#U", 7)) // U+0007, omit the non-printable character
%e: with lower-case e, e.g. -1234.456e+78
%E: with upper-case E, e.g. -1234.456E+78
console.log(sprintf("%e", 1.1)) // 1.100000e+0
console.log(sprintf("%0.20e", 1.1)) // 1.00000000000000000000e+9
console.log(sprintf("%E", 1.1)) // 1.100000E+0
Default precision is 6.
%F is synonym for %f.
console.log(sprintf("%f", 1.0)) // 1.000000
console.log(sprintf("%.f", 1.0)) // 1
console.log(sprintf("%4.f", 1.0)) // ' 1'
console.log(sprintf("%5.2f", 1.235)) // ' 1.24'
console.log(sprintf("%5.2f", -1.235)) // '-1.23'
Align to the left:
console.log(sprintf("%-5.2f", 1.0)) // '1.00 '
Padding '0' on the left:
console.log(sprintf("%010.6f", -1.235)) // -01.235000
Round to precision:
console.log(sprintf("%.2f", 1)) // 1.00
console.log(sprintf("%.2f", -1.235)) // -1.23
%g: whichever of %e or %f produces more compact output. %G: using 'E' in scientific notation.
console.log(sprintf("%g", 1)) // 1
console.log(sprintf("%g", 1.234)) // 1.234
console.log(sprintf("%.3g", 1.234)) // 1.23, precision 被用来表示总有效位数
console.log(sprintf("%g", 6666666.6)) // 6.6666666e+6，整数部分 7 位以上转科学计数法
console.log(sprintf("%.3g", 6666666.6)) // 6.67e+6，precision 为科学计数法的小数部分的总有效位数
console.log(sprintf("%.g", 6666666.6)) // 7e+6，precision 为 0 时
Operand's string output conform to the definitions of width, precision and flags.
console.log(sprintf("%s", 1)) // any type will be convert to string
console.log(sprintf("%4.2s", 123456)) // ' 12', precision in '%s' means maximum width to the operand's string representation
%p is for pointer in golang, there is no counterpart in Javascript.
%Z: Show the size by byte:
console.log(sprintf("%Z", 1024)) // 1.00 kB, default is base 2，1024=1k
console.log(sprintf("%Z", 1024 * 1024)) // 1.00 MB
console.log(sprintf("%.1Z", 1024 * 1024)) // 1.0 MB
console.log(sprintf("%#Z", 1000 * 1000)) // 1.00 MB, flag '#' base 10，1000=1k
%z: Show the size by bits:
console.log(sprintf("%z", 1024)) // 8.00 kb, default is base 2，1024=1k
console.log(sprintf("%z", 1024 * 1024)) // 8.00 Mb
console.log(sprintf("%#z", 1000 * 1000)) // 8.00 Mb, flag '#' base 10，1000=1k
In sprintf, the default behavior is for each formatting verb to format successive arguments passed in the call. However, the notation [n] immediately before the verb indicates that the nth one-indexed argument is to be formatted instead. The same notation before a '*' for a width or precision selects the argument index holding the value. After processing a bracketed expression [n], arguments n+1, n+2, etc. will be processed unless otherwise directed.
For example,
sprintf("%[2]d %[1]d\n", 11, 22)
will yield "22, 11" (index from 1), while
sprintf("%[3]*.[2]*[1]f", 12.0, 2, 6)
equivalent to
sprintf("%6.2f", 12.0)
will yield " 12.00".
Because an explicit index affects subsequent verbs, this notation can be used to print the same values multiple times by resetting the index for the first argument to be repeated:
sprintf("%d %d %#[1]x %#x", 16, 17)
will yield "16 17 0x10 0x11".
FAQs
A golang `fmt.Printf` implementation
The npm package gofmt receives a total of 18 weekly downloads. As such, gofmt popularity was classified as not popular.
We found that gofmt demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
Security News
Research
A supply chain attack on Rspack's npm packages injected cryptomining malware, potentially impacting thousands of developers.
Research
Security News
Socket researchers discovered a malware campaign on npm delivering the Skuld infostealer via typosquatted packages, exposing sensitive data.
Security News
Sonar’s acquisition of Tidelift highlights a growing industry shift toward sustainable open source funding, addressing maintainer burnout and critical software dependencies.