PHP's json_encode in TypeScript

✓ Verified: PHP 8.3
Examples tested against actual runtime. CI re-verifies continuously. Only documented examples are tested.

How to use

Install via yarn add locutus and import: import { json_encode } from 'locutus/php/json/json_encode'.

Or with CommonJS: const { json_encode } = require('locutus/php/json/json_encode')

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.

#codeexpected result
1json_encode('Kevin')'"Kevin"'

Dependencies

This function uses the following Locutus functions:

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

import { setPhpRuntimeEntry } from '../_helpers/_phpRuntimeState.ts'
import type { PhpAssoc, PhpRuntimeValue } from '../_helpers/_phpTypes.ts'

type JsonPrimitive = string | number | boolean | null
type JsonObject = { [key: string]: JsonValue }
type JsonValue = JsonPrimitive | JsonValue[] | JsonObject
type JsonEncodeInput = PhpRuntimeValue

const isJsonObject = (value: PhpRuntimeValue): value is JsonObject =>
typeof value === 'object' && value !== null && !Array.isArray(value)

export function json_encode(mixedVal: JsonEncodeInput): string | null {
// discuss at: https://phpjs.org/functions/json_encode/
// parity verified: PHP 8.3
// original by: Public Domain (https://www.json.org/json2.js)
// reimplemented by: Kevin van Zonneveld (https://kevin.vanzonneveld.net)
// improved by: Michael White
// input by: felix
// bugfixed by: Brett Zamir (https://brett-zamir.me)
// example 1: json_encode('Kevin')
// returns 1: '"Kevin"'

/*
https://www.JSON.org/json2.js
2008-11-19
Public Domain.
NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
See https://www.JSON.org/js.html
*/

const json = typeof JSON === 'object' && JSON !== null ? JSON : null
let retVal
try {
if (typeof json === 'object' && json !== null) {
const stringify = json.stringify
if (typeof stringify === 'function') {
// Errors will not be caught here if our own equivalent to resource
retVal = stringify.call(json, mixedVal)
if (retVal === undefined) {
throw new SyntaxError('json_encode')
}
return retVal
}
}

const value = mixedVal

const quote = function (string: string): string {
const escapeChars = [
'\u0000-\u001f',
'\u007f-\u009f',
'\u00ad',
'\u0600-\u0604',
'\u070f',
'\u17b4',
'\u17b5',
'\u200c-\u200f',
'\u2028-\u202f',
'\u2060-\u206f',
'\ufeff',
'\ufff0-\uffff',
].join('')
const escapable = new RegExp('[\\"' + escapeChars + ']', 'g')
const meta: Record<string, string> = {
// table of character substitutions
'\b': '\\b',
'\t': '\\t',
'\n': '\\n',
'\f': '\\f',
'\r': '\\r',
'"': '\\"',
'\\': '\\\\',
}

escapable.lastIndex = 0
return escapable.test(string)
? '"' +
string.replace(escapable, function (a) {
const c = meta[a]
return typeof c === 'string' ? c : '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4)
}) +
'"'
: '"' + string + '"'
}

const _str = function (
key: string | number,
holder: PhpAssoc<PhpRuntimeValue> | PhpRuntimeValue[],
): string | undefined {
let gap = ''
const indent = ' '
// The loop counter.
let i = 0
// The member key.
let k = ''
// The member value.
let v = ''
let length = 0
const mind = gap
let partial: string[] = []
let value = Array.isArray(holder) ? holder[Number(key)] : holder[String(key)]

// If the value has a toJSON method, call it to obtain a replacement value.
if (typeof value === 'object' && value !== null) {
if ('toJSON' in value && typeof value.toJSON === 'function') {
value = value.toJSON.call(value, key)
}
}

// What happens next depends on the value's type.
switch (typeof value) {
case 'string':
return quote(value)

case 'number':
// JSON numbers must be finite. Encode non-finite numbers as null.
return isFinite(value) ? String(value) : 'null'

case 'boolean':
// If the value is a boolean or null, convert it to a string.
return String(value)

case 'object':
// If the type is 'object', we might be dealing with an object or an array or
// null.
// Due to a specification blunder in ECMAScript, typeof null is 'object',
// so watch out for that case.
if (!value) {
return 'null'
}

// Make an array to hold the partial results of stringifying this object value.
gap += indent
partial = []

// Is the value an array?
if (Array.isArray(value)) {
// The value is an array. Stringify every element. Use null as a placeholder
// for non-JSON values.
length = value.length
for (i = 0; i < length; i += 1) {
partial[i] = _str(i, value) || 'null'
}

// Join all of the elements together, separated with commas, and wrap them in
// brackets.
v =
partial.length === 0
? '[]'
: gap
? '[\n' + gap + partial.join(',\n' + gap) + '\n' + mind + ']'
: '[' + partial.join(',') + ']'
// gap = mind // not used
return v
}

// Iterate through all of the keys in the object.
if (!isJsonObject(value)) {
throw new SyntaxError('json_encode')
}
for (const [entryKey] of Object.entries(value)) {
k = entryKey
v = _str(k, value) || ''
if (v) {
partial.push(quote(k) + (gap ? ': ' : ':') + v)
}
}

// Join all of the member texts together, separated with commas,
// and wrap them in braces.
v =
partial.length === 0
? '{}'
: gap
? '{\n' + gap + partial.join(',\n' + gap) + '\n' + mind + '}'
: '{' + partial.join(',') + '}'
// gap = mind // Not used
return v
case 'undefined':
case 'function':
default:
throw new SyntaxError('json_encode')
}
}

// Make a fake root object containing our value under the key of ''.
// Return the result of stringifying the value.
const encoded = _str('', {
'': value,
})
if (typeof encoded !== 'string') {
throw new SyntaxError('json_encode')
}
return encoded
} catch (err) {
// @todo: ensure error handling above throws a SyntaxError in all cases where it could
// (i.e., when the JSON global is not available and there is an error)
if (!(err instanceof SyntaxError)) {
throw new Error('Unexpected error type in json_encode()')
}
// usable by json_last_error()
setPhpRuntimeEntry('last_error_json', 4)
return null
}
}

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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