PHP's sprintf in TypeScript

How to use

Install via yarn add locutus and import: import { sprintf } from 'locutus/php/strings/sprintf'.

Or with CommonJS: const { sprintf } = require('locutus/php/strings/sprintf')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	sprintf("%01.2f", 123.1)	'123.10'
2	sprintf("[%10s]", 'monkey')	'[ monkey]'
3	sprintf("[%'#10s]", 'monkey')	'[####monkey]'
4	sprintf("%d", 123456789012345)	'123456789012345'
5	sprintf('%-03s', 'E')	'E00'
6	sprintf('%+010d', 9)	'+000000009'
7	sprintf('%+0\'@10d', 9)	'@@@@@@@@+9'
8	sprintf('%.f', 3.14)	'3.140000'
9	sprintf('%% %2$d', 1, 2)	'% 2'

Here's what our current TypeScript equivalent to PHP's sprintf looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

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import type { PhpRuntimeValue } from '../_helpers/_phpTypes.ts'

type SprintfValue = PhpRuntimeValue

export function sprintf(format: string, ...args: SprintfValue[]): string | false {
  //      discuss at: https://locutus.io/php/sprintf/
  // parity verified: PHP 8.3
  //     original by: Ash Searle (https://hexmen.com/blog/)
  //     improved by: Michael White (https://getsprink.com)
  //     improved by: Jack
  //     improved by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: Dj
  //     improved by: Allidylls
  //        input by: Paulo Freitas
  //        input by: Brett Zamir (https://brett-zamir.me)
  //     improved by: Rafał Kukawski (https://kukawski.pl)
  //       example 1: sprintf("%01.2f", 123.1)
  //       returns 1: '123.10'
  //       example 2: sprintf("[%10s]", 'monkey')
  //       returns 2: '[    monkey]'
  //       example 3: sprintf("[%'#10s]", 'monkey')
  //       returns 3: '[####monkey]'
  //       example 4: sprintf("%d", 123456789012345)
  //       returns 4: '123456789012345'
  //       example 5: sprintf('%-03s', 'E')
  //       returns 5: 'E00'
  //       example 6: sprintf('%+010d', 9)
  //       returns 6: '+000000009'
  //       example 7: sprintf('%+0\'@10d', 9)
  //       returns 7: '@@@@@@@@+9'
  //       example 8: sprintf('%.f', 3.14)
  //       returns 8: '3.140000'
  //       example 9: sprintf('%% %2$d', 1, 2)
  //       returns 9: '% 2'

  const regex = /%%|%(?:(\d+)\$)?((?:[-+#0 ]|'[\s\S])*)(\d+)?(?:\.(\d*))?([\s\S])/g
  const callArgs: SprintfValue[] = [format, ...args]
  let i = 1

  const _pad = function (str: string, len: number, chr: string, leftJustify: boolean): string {
    if (!chr) {
      chr = ' '
    }
    const padding = str.length >= len ? '' : new Array((1 + len - str.length) >>> 0).join(chr)
    return leftJustify ? str + padding : padding + str
  }

  const justify = function (
    value: string,
    prefix: string,
    leftJustify: boolean,
    minWidth: number,
    padChar: string,
  ): string {
    const diff = minWidth - value.length
    if (diff > 0) {
      // when padding with zeros
      // on the left side
      // keep sign (+ or -) in front
      if (!leftJustify && padChar === '0') {
        value = [value.slice(0, prefix.length), _pad('', diff, '0', true), value.slice(prefix.length)].join('')
      } else {
        value = _pad(value, minWidth, padChar, leftJustify)
      }
    }
    return value
  }

  const _formatBaseX = function (
    value: SprintfValue,
    base: number,
    leftJustify: boolean,
    minWidth: number,
    precision: number | undefined,
    padChar: string,
  ): string {
    // Note: casts negative numbers to positive ones
    const number = Number(value) >>> 0
    const padded = _pad(number.toString(base), precision || 0, '0', false)
    return justify(padded, '', leftJustify, minWidth, padChar)
  }

  // _formatString()
  const _formatString = function (
    value: string,
    leftJustify: boolean,
    minWidth: number,
    precision: number | null | undefined,
    customPadChar: string,
  ) {
    if (precision !== null && precision !== undefined) {
      value = value.slice(0, precision)
    }
    return justify(value, '', leftJustify, minWidth, customPadChar)
  }

  // doFormat()
  const doFormat = function (
    substring: string,
    argIndex: string | undefined,
    modifiers: string,
    minWidthRaw: string | undefined,
    precisionRaw: string | undefined,
    specifier: string,
  ): string {
    let number = 0
    let prefix = ''
    let value: SprintfValue

    if (substring === '%%') {
      return '%'
    }

    // parse modifiers
    let padChar = ' ' // pad with spaces by default
    let leftJustify = false
    let positiveNumberPrefix = ''
    let j = 0
    let l = 0

    for (j = 0, l = modifiers.length; j < l; j++) {
      switch (modifiers.charAt(j)) {
        case ' ':
        case '0':
          padChar = modifiers.charAt(j)
          break
        case '+':
          positiveNumberPrefix = '+'
          break
        case '-':
          leftJustify = true
          break
        case "'":
          if (j + 1 < l) {
            padChar = modifiers.charAt(j + 1)
            j++
          }
          break
      }
    }

    let minWidthNum = 0
    if (!minWidthRaw) {
      minWidthNum = 0
    } else {
      minWidthNum = +minWidthRaw
    }

    if (!isFinite(minWidthNum)) {
      throw new Error('Width must be finite')
    }

    let precisionNum: number | undefined
    if (!precisionRaw) {
      precisionNum = specifier === 'd' ? 0 : 'fFeE'.includes(specifier) ? 6 : undefined
    } else {
      precisionNum = +precisionRaw
    }

    if (argIndex && +argIndex === 0) {
      throw new Error('Argument number must be greater than zero')
    }

    if (argIndex && +argIndex >= callArgs.length) {
      throw new Error('Too few arguments')
    }

    value = argIndex ? callArgs[+argIndex] : callArgs[i++]

    switch (specifier) {
      case '%':
        return '%'
      case 's':
        return _formatString(String(value), leftJustify, minWidthNum, precisionNum, padChar)
      case 'c':
        return _formatString(String.fromCharCode(+String(value)), leftJustify, minWidthNum, precisionNum, padChar)
      case 'b':
        return _formatBaseX(value, 2, leftJustify, minWidthNum, precisionNum, padChar)
      case 'o':
        return _formatBaseX(value, 8, leftJustify, minWidthNum, precisionNum, padChar)
      case 'x':
        return _formatBaseX(value, 16, leftJustify, minWidthNum, precisionNum, padChar)
      case 'X':
        return _formatBaseX(value, 16, leftJustify, minWidthNum, precisionNum, padChar).toUpperCase()
      case 'u':
        return _formatBaseX(value, 10, leftJustify, minWidthNum, precisionNum, padChar)
      case 'i':
      case 'd':
        number = +String(value) || 0
        // Plain Math.round doesn't just truncate
        number = Math.round(number - (number % 1))
        prefix = number < 0 ? '-' : positiveNumberPrefix
        value = prefix + _pad(String(Math.abs(number)), precisionNum ?? 0, '0', false)

        if (leftJustify && padChar === '0') {
          // can't right-pad 0s on integers
          padChar = ' '
        }
        return justify(String(value), prefix, leftJustify, minWidthNum, padChar)
      case 'e':
      case 'E':
      case 'f': // @todo: Should handle locales (as per setlocale)
      case 'F':
      case 'g':
      case 'G': {
        number = +String(value)
        prefix = number < 0 ? '-' : positiveNumberPrefix
        const methodIndex = 'efg'.indexOf(specifier.toLowerCase())
        const absNumber = Math.abs(number)
        let floatResult = ''
        if (methodIndex === 0) {
          floatResult = absNumber.toExponential(precisionNum)
        } else if (methodIndex === 1) {
          floatResult = absNumber.toFixed(precisionNum)
        } else {
          floatResult = absNumber.toPrecision(precisionNum)
        }
        const justified = justify(prefix + floatResult, prefix, leftJustify, minWidthNum, padChar)
        return 'eEfFgG'.indexOf(specifier) % 2 === 0 ? justified : justified.toUpperCase()
      }
      default:
        // unsupported specifier, consume that char and return empty
        return ''
    }
  }

  try {
    return format.replace(regex, doFormat)
  } catch (_err) {
    return false
  }
}

export function sprintf(format, ...args) {
  //      discuss at: https://locutus.io/php/sprintf/
  // parity verified: PHP 8.3
  //     original by: Ash Searle (https://hexmen.com/blog/)
  //     improved by: Michael White (https://getsprink.com)
  //     improved by: Jack
  //     improved by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: Dj
  //     improved by: Allidylls
  //        input by: Paulo Freitas
  //        input by: Brett Zamir (https://brett-zamir.me)
  //     improved by: Rafał Kukawski (https://kukawski.pl)
  //       example 1: sprintf("%01.2f", 123.1)
  //       returns 1: '123.10'
  //       example 2: sprintf("[%10s]", 'monkey')
  //       returns 2: '[    monkey]'
  //       example 3: sprintf("[%'#10s]", 'monkey')
  //       returns 3: '[####monkey]'
  //       example 4: sprintf("%d", 123456789012345)
  //       returns 4: '123456789012345'
  //       example 5: sprintf('%-03s', 'E')
  //       returns 5: 'E00'
  //       example 6: sprintf('%+010d', 9)
  //       returns 6: '+000000009'
  //       example 7: sprintf('%+0\'@10d', 9)
  //       returns 7: '@@@@@@@@+9'
  //       example 8: sprintf('%.f', 3.14)
  //       returns 8: '3.140000'
  //       example 9: sprintf('%% %2$d', 1, 2)
  //       returns 9: '% 2'

  const regex = /%%|%(?:(\d+)\$)?((?:[-+#0 ]|'[\s\S])*)(\d+)?(?:\.(\d*))?([\s\S])/g
  const callArgs = [format, ...args]
  let i = 1

  const _pad = function (str, len, chr, leftJustify) {
    if (!chr) {
      chr = ' '
    }
    const padding = str.length >= len ? '' : new Array((1 + len - str.length) >>> 0).join(chr)
    return leftJustify ? str + padding : padding + str
  }

  const justify = function (value, prefix, leftJustify, minWidth, padChar) {
    const diff = minWidth - value.length
    if (diff > 0) {
      // when padding with zeros
      // on the left side
      // keep sign (+ or -) in front
      if (!leftJustify && padChar === '0') {
        value = [value.slice(0, prefix.length), _pad('', diff, '0', true), value.slice(prefix.length)].join('')
      } else {
        value = _pad(value, minWidth, padChar, leftJustify)
      }
    }
    return value
  }

  const _formatBaseX = function (value, base, leftJustify, minWidth, precision, padChar) {
    // Note: casts negative numbers to positive ones
    const number = Number(value) >>> 0
    const padded = _pad(number.toString(base), precision || 0, '0', false)
    return justify(padded, '', leftJustify, minWidth, padChar)
  }

  // _formatString()
  const _formatString = function (value, leftJustify, minWidth, precision, customPadChar) {
    if (precision !== null && precision !== undefined) {
      value = value.slice(0, precision)
    }
    return justify(value, '', leftJustify, minWidth, customPadChar)
  }

  // doFormat()
  const doFormat = function (substring, argIndex, modifiers, minWidthRaw, precisionRaw, specifier) {
    let number = 0
    let prefix = ''
    let value

    if (substring === '%%') {
      return '%'
    }

    // parse modifiers
    let padChar = ' ' // pad with spaces by default
    let leftJustify = false
    let positiveNumberPrefix = ''
    let j = 0
    let l = 0

    for (j = 0, l = modifiers.length; j < l; j++) {
      switch (modifiers.charAt(j)) {
        case ' ':
        case '0':
          padChar = modifiers.charAt(j)
          break
        case '+':
          positiveNumberPrefix = '+'
          break
        case '-':
          leftJustify = true
          break
        case "'":
          if (j + 1 < l) {
            padChar = modifiers.charAt(j + 1)
            j++
          }
          break
      }
    }

    let minWidthNum = 0
    if (!minWidthRaw) {
      minWidthNum = 0
    } else {
      minWidthNum = +minWidthRaw
    }

    if (!isFinite(minWidthNum)) {
      throw new Error('Width must be finite')
    }

    let precisionNum
    if (!precisionRaw) {
      precisionNum = specifier === 'd' ? 0 : 'fFeE'.includes(specifier) ? 6 : undefined
    } else {
      precisionNum = +precisionRaw
    }

    if (argIndex && +argIndex === 0) {
      throw new Error('Argument number must be greater than zero')
    }

    if (argIndex && +argIndex >= callArgs.length) {
      throw new Error('Too few arguments')
    }

    value = argIndex ? callArgs[+argIndex] : callArgs[i++]

    switch (specifier) {
      case '%':
        return '%'
      case 's':
        return _formatString(String(value), leftJustify, minWidthNum, precisionNum, padChar)
      case 'c':
        return _formatString(String.fromCharCode(+String(value)), leftJustify, minWidthNum, precisionNum, padChar)
      case 'b':
        return _formatBaseX(value, 2, leftJustify, minWidthNum, precisionNum, padChar)
      case 'o':
        return _formatBaseX(value, 8, leftJustify, minWidthNum, precisionNum, padChar)
      case 'x':
        return _formatBaseX(value, 16, leftJustify, minWidthNum, precisionNum, padChar)
      case 'X':
        return _formatBaseX(value, 16, leftJustify, minWidthNum, precisionNum, padChar).toUpperCase()
      case 'u':
        return _formatBaseX(value, 10, leftJustify, minWidthNum, precisionNum, padChar)
      case 'i':
      case 'd':
        number = +String(value) || 0
        // Plain Math.round doesn't just truncate
        number = Math.round(number - (number % 1))
        prefix = number < 0 ? '-' : positiveNumberPrefix
        value = prefix + _pad(String(Math.abs(number)), precisionNum ?? 0, '0', false)

        if (leftJustify && padChar === '0') {
          // can't right-pad 0s on integers
          padChar = ' '
        }
        return justify(String(value), prefix, leftJustify, minWidthNum, padChar)
      case 'e':
      case 'E':
      case 'f': // @todo: Should handle locales (as per setlocale)
      case 'F':
      case 'g':
      case 'G': {
        number = +String(value)
        prefix = number < 0 ? '-' : positiveNumberPrefix
        const methodIndex = 'efg'.indexOf(specifier.toLowerCase())
        const absNumber = Math.abs(number)
        let floatResult = ''
        if (methodIndex === 0) {
          floatResult = absNumber.toExponential(precisionNum)
        } else if (methodIndex === 1) {
          floatResult = absNumber.toFixed(precisionNum)
        } else {
          floatResult = absNumber.toPrecision(precisionNum)
        }
        const justified = justify(prefix + floatResult, prefix, leftJustify, minWidthNum, padChar)
        return 'eEfFgG'.indexOf(specifier) % 2 === 0 ? justified : justified.toUpperCase()
      }
      default:
        // unsupported specifier, consume that char and return empty
        return ''
    }
  }

  try {
    return format.replace(regex, doFormat)
  } catch (_err) {
    return false
  }
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

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