jsesc

Given some data, jsesc returns a stringified representation
of that data. jsesc is similar to JSON.stringify()
except:
- it outputs JavaScript instead of JSON by default, enabling support for data structures like ES6 maps and sets;
- it offers many options to customize the output;
- its output is ASCII-safe by default, thanks to its use of escape sequences where needed.
For any input, jsesc generates the shortest possible valid printable-ASCII-only output. Here’s an online demo.
jsesc’s output can be used instead of JSON.stringify’s
to avoid mojibake
and other encoding issues, or even to avoid
errors when passing JSON-formatted data (which may contain U+2028
LINE SEPARATOR, U+2029 PARAGRAPH SEPARATOR, or lone
surrogates) to a JavaScript parser or an UTF-8 encoder.
Installation
Via npm:
npm install jsescIn Node.js:
const jsesc = require('jsesc');API
jsesc(value, options)
This function takes a value and returns an escaped version of the value where any characters that are not printable ASCII symbols are escaped using the shortest possible (but valid) escape sequences for use in JavaScript strings. The first supported value type is strings:
jsesc('Ich ♥ Bücher');
// → 'Ich \\u2665 B\\xFCcher'
jsesc('foo 𝌆 bar');
// → 'foo \\uD834\\uDF06 bar'Instead of a string, the value can also be an array, an
object, a map, a set, or a buffer. In such cases, jsesc
returns a stringified version of the value where any characters that are
not printable ASCII symbols are escaped in the same way.
// Escaping an array
jsesc([
'Ich ♥ Bücher', 'foo 𝌆 bar'
]);
// → '[\'Ich \\u2665 B\\xFCcher\',\'foo \\uD834\\uDF06 bar\']'
// Escaping an object
jsesc({
'Ich ♥ Bücher': 'foo 𝌆 bar'
});
// → '{\'Ich \\u2665 B\\xFCcher\':\'foo \\uD834\\uDF06 bar\'}'The optional options argument accepts an object with the
following options:
quotes
The default value for the quotes option is
'single'. This means that any occurrences of '
in the input string are escaped as \', so that the output
can be used in a string literal wrapped in single quotes.
jsesc('`Lorem` ipsum "dolor" sit \'amet\' etc.');
// → 'Lorem ipsum "dolor" sit \\\'amet\\\' etc.'
jsesc('`Lorem` ipsum "dolor" sit \'amet\' etc.', {
'quotes': 'single'
});
// → '`Lorem` ipsum "dolor" sit \\\'amet\\\' etc.'
// → "`Lorem` ipsum \"dolor\" sit \\'amet\\' etc."If you want to use the output as part of a string literal wrapped in
double quotes, set the quotes option to
'double'.
jsesc('`Lorem` ipsum "dolor" sit \'amet\' etc.', {
'quotes': 'double'
});
// → '`Lorem` ipsum \\"dolor\\" sit \'amet\' etc.'
// → "`Lorem` ipsum \\\"dolor\\\" sit 'amet' etc."If you want to use the output as part of a template literal
(i.e. wrapped in backticks), set the quotes option to
'backtick'.
jsesc('`Lorem` ipsum "dolor" sit \'amet\' etc.', {
'quotes': 'backtick'
});
// → '\\`Lorem\\` ipsum "dolor" sit \'amet\' etc.'
// → "\\`Lorem\\` ipsum \"dolor\" sit 'amet' etc."
// → `\\\`Lorem\\\` ipsum "dolor" sit 'amet' etc.`This setting also affects the output for arrays and objects:
jsesc({ 'Ich ♥ Bücher': 'foo 𝌆 bar' }, {
'quotes': 'double'
});
// → '{"Ich \\u2665 B\\xFCcher":"foo \\uD834\\uDF06 bar"}'
jsesc([ 'Ich ♥ Bücher', 'foo 𝌆 bar' ], {
'quotes': 'double'
});
// → '["Ich \\u2665 B\\xFCcher","foo \\uD834\\uDF06 bar"]'numbers
The default value for the numbers option is
'decimal'. This means that any numeric values are
represented using decimal integer literals. Other valid options are
binary, octal, and hexadecimal,
which result in binary integer literals, octal integer literals, and
hexadecimal integer literals, respectively.
jsesc(42, {
'numbers': 'binary'
});
// → '0b101010'
jsesc(42, {
'numbers': 'octal'
});
// → '0o52'
jsesc(42, {
'numbers': 'decimal'
});
// → '42'
jsesc(42, {
'numbers': 'hexadecimal'
});
// → '0x2A'wrap
The wrap option takes a boolean value (true
or false), and defaults to false (disabled).
When enabled, the output is a valid JavaScript string literal wrapped in
quotes. The type of quotes can be specified through the
quotes setting.
jsesc('Lorem ipsum "dolor" sit \'amet\' etc.', {
'quotes': 'single',
'wrap': true
});
// → '\'Lorem ipsum "dolor" sit \\\'amet\\\' etc.\''
// → "\'Lorem ipsum \"dolor\" sit \\\'amet\\\' etc.\'"
jsesc('Lorem ipsum "dolor" sit \'amet\' etc.', {
'quotes': 'double',
'wrap': true
});
// → '"Lorem ipsum \\"dolor\\" sit \'amet\' etc."'
// → "\"Lorem ipsum \\\"dolor\\\" sit \'amet\' etc.\""es6
The es6 option takes a boolean value (true
or false), and defaults to false (disabled).
When enabled, any astral Unicode symbols in the input are escaped using
ECMAScript
6 Unicode code point escape sequences instead of using separate
escape sequences for each surrogate half. If backwards compatibility
with ES5 environments is a concern, don’t enable this setting. If the
json setting is enabled, the value for the es6
setting is ignored (as if it was false).
// By default, the `es6` option is disabled:
jsesc('foo 𝌆 bar 💩 baz');
// → 'foo \\uD834\\uDF06 bar \\uD83D\\uDCA9 baz'
// To explicitly disable it:
jsesc('foo 𝌆 bar 💩 baz', {
'es6': false
});
// → 'foo \\uD834\\uDF06 bar \\uD83D\\uDCA9 baz'
// To enable it:
jsesc('foo 𝌆 bar 💩 baz', {
'es6': true
});
// → 'foo \\u{1D306} bar \\u{1F4A9} baz'escapeEverything
The escapeEverything option takes a boolean value
(true or false), and defaults to
false (disabled). When enabled, all the symbols in the
output are escaped — even printable ASCII symbols.
jsesc('lolwat"foo\'bar', {
'escapeEverything': true
});
// → '\\x6C\\x6F\\x6C\\x77\\x61\\x74\\"\\x66\\x6F\\x6F\\\'\\x62\\x61\\x72'
// → "\\x6C\\x6F\\x6C\\x77\\x61\\x74\\\"\\x66\\x6F\\x6F\\'\\x62\\x61\\x72"This setting also affects the output for string literals within arrays and objects.
minimal
The minimal option takes a boolean value
(true or false), and defaults to
false (disabled). When enabled, only a limited set of
symbols in the output are escaped:
- U+0000
\0 - U+0008
\b - U+0009
\t - U+000A
\n - U+000C
\f - U+000D
\r - U+005C
\\ - U+2028
\u2028 - U+2029
\u2029 - whatever symbol is being used for wrapping string literals (based on
the
quotesoption)
Note: with this option enabled, jsesc output is no longer guaranteed to be ASCII-safe.
jsesc('foo\u2029bar\nbaz©qux𝌆flops', {
'minimal': false
});
// → 'foo\\u2029bar\\nbaz©qux𝌆flops'isScriptContext
The isScriptContext option takes a boolean value
(true or false), and defaults to
false (disabled). When enabled, occurrences of </script and
</style in the output are escaped as
<\/script and <\/style, and <!--
is escaped as \x3C!-- (or \u003C!-- when the
json option is enabled). This setting is useful when
jsesc’s output ends up as part of a <script> or
<style> element in an HTML document.
jsesc('foo</script>bar', {
'isScriptContext': true
});
// → 'foo<\\/script>bar'compact
The compact option takes a boolean value
(true or false), and defaults to
true (enabled). When enabled, the output for arrays and
objects is as compact as possible; it’s not formatted nicely.
jsesc({ 'Ich ♥ Bücher': 'foo 𝌆 bar' }, {
'compact': true // this is the default
});
// → '{\'Ich \u2665 B\xFCcher\':\'foo \uD834\uDF06 bar\'}'
jsesc({ 'Ich ♥ Bücher': 'foo 𝌆 bar' }, {
'compact': false
});
// → '{\n\t\'Ich \u2665 B\xFCcher\': \'foo \uD834\uDF06 bar\'\n}'
jsesc([ 'Ich ♥ Bücher', 'foo 𝌆 bar' ], {
'compact': false
});
// → '[\n\t\'Ich \u2665 B\xFCcher\',\n\t\'foo \uD834\uDF06 bar\'\n]'This setting has no effect on the output for strings.
indent
The indent option takes a string value, and defaults to
'\t'. When the compact setting is enabled
(true), the value of the indent option is used
to format the output for arrays and objects.
jsesc({ 'Ich ♥ Bücher': 'foo 𝌆 bar' }, {
'compact': false,
'indent': '\t' // this is the default
});
// → '{\n\t\'Ich \u2665 B\xFCcher\': \'foo \uD834\uDF06 bar\'\n}'
jsesc({ 'Ich ♥ Bücher': 'foo 𝌆 bar' }, {
'compact': false,
'indent': ' '
});
// → '{\n \'Ich \u2665 B\xFCcher\': \'foo \uD834\uDF06 bar\'\n}'
jsesc([ 'Ich ♥ Bücher', 'foo 𝌆 bar' ], {
'compact': false,
'indent': ' '
});
// → '[\n \'Ich \u2665 B\xFCcher\',\n\ t\'foo \uD834\uDF06 bar\'\n]'This setting has no effect on the output for strings.
indentLevel
The indentLevel option takes a numeric value, and
defaults to 0. It represents the current indentation level,
i.e. the number of times the value of the
indent option is repeated.
jsesc(['a', 'b', 'c'], {
'compact': false,
'indentLevel': 1
});
// → '[\n\t\t\'a\',\n\t\t\'b\',\n\t\t\'c\'\n\t]'
jsesc(['a', 'b', 'c'], {
'compact': false,
'indentLevel': 2
});
// → '[\n\t\t\t\'a\',\n\t\t\t\'b\',\n\t\t\t\'c\'\n\t\t]'json
The json option takes a boolean value (true
or false), and defaults to false (disabled).
When enabled, the output is valid JSON. Hexadecimal
character escape sequences and the
\v or \0 escape sequences are not used.
Setting json: true implies
quotes: 'double', wrap: true, es6: false, although these
values can still be overridden if needed — but in such cases, the output
won’t be valid JSON anymore.
jsesc('foo\x00bar\xFF\uFFFDbaz', {
'json': true
});
// → '"foo\\u0000bar\\u00FF\\uFFFDbaz"'
jsesc({ 'foo\x00bar\xFF\uFFFDbaz': 'foo\x00bar\xFF\uFFFDbaz' }, {
'json': true
});
// → '{"foo\\u0000bar\\u00FF\\uFFFDbaz":"foo\\u0000bar\\u00FF\\uFFFDbaz"}'
jsesc([ 'foo\x00bar\xFF\uFFFDbaz', 'foo\x00bar\xFF\uFFFDbaz' ], {
'json': true
});
// → '["foo\\u0000bar\\u00FF\\uFFFDbaz","foo\\u0000bar\\u00FF\\uFFFDbaz"]'
// Values that are acceptable in JSON but aren’t strings, arrays, or object
// literals can’t be escaped, so they’ll just be preserved:
jsesc([ 'foo\x00bar', [1, '©', { 'foo': true, 'qux': null }], 42 ], {
'json': true
});
// → '["foo\\u0000bar",[1,"\\u00A9",{"foo":true,"qux":null}],42]'
// Values that aren’t allowed in JSON are run through `JSON.stringify()`:
jsesc([ undefined, -Infinity ], {
'json': true
});
// → '[null,null]'Note: Using this option on objects or arrays that
contain non-string values relies on JSON.stringify(). For
legacy environments like IE ≤ 7, use a JSON
polyfill.
lowercaseHex
The lowercaseHex option takes a boolean value
(true or false), and defaults to
false (disabled). When enabled, any alphabetical
hexadecimal digits in escape sequences as well as any hexadecimal
integer literals (see the numbers
option) in the output are in lowercase.
jsesc('Ich ♥ Bücher', {
'lowercaseHex': true
});
// → 'Ich \\u2665 B\\xfccher'
// ^^
jsesc(42, {
'numbers': 'hexadecimal',
'lowercaseHex': true
});
// → '0x2a'
// ^^jsesc.version
A string representing the semantic version number.
Using the jsesc binary
To use the jsesc binary in your shell, simply install
jsesc globally using npm:
npm install -g jsescAfter that you’re able to escape strings from the command line:
$ jsesc 'föo ♥ bår 𝌆 baz'
f\xF6o \u2665 b\xE5r \uD834\uDF06 bazTo escape arrays or objects containing string values, use the
-o/--object option:
$ jsesc --object '{ "föo": "♥", "bår": "𝌆 baz" }'
{'f\xF6o':'\u2665','b\xE5r':'\uD834\uDF06 baz'}To prettify the output in such cases, use the
-p/--pretty option:
$ jsesc --pretty '{ "föo": "♥", "bår": "𝌆 baz" }'
{
'f\xF6o': '\u2665',
'b\xE5r': '\uD834\uDF06 baz'
}For valid JSON output, use the -j/--json
option:
$ jsesc --json --pretty '{ "föo": "♥", "bår": "𝌆 baz" }'
{
"f\u00F6o": "\u2665",
"b\u00E5r": "\uD834\uDF06 baz"
}Read a local JSON file, escape any non-ASCII symbols, and save the result to a new file:
$ jsesc --json --object < data-raw.json > data-escaped.jsonOr do the same with an online JSON file:
$ curl -sL "http://git.io/aorKgQ" | jsesc --json --object > data-escaped.jsonSee jsesc --help for the full list of options.
Support
As of v2.0.0, jsesc supports Node.js v4+ only.
Older versions (up to jsesc v1.3.0) support Chrome 27, Firefox 3,
Safari 4, Opera 10, IE 6, Node.js v6.0.0, Narwhal 0.3.2, RingoJS
0.8-0.11, PhantomJS 1.9.0, and Rhino 1.7RC4. Note:
Using the json option on objects or arrays that contain
non-string values relies on JSON.parse(). For legacy
environments like IE ≤ 7, use a JSON
polyfill.
Author
| Mathias Bynens |
License
This library is available under the MIT license.