Polyfills, Ponyfills, and Transpiling

When discussing new JavaScript features and syntax, it’s common to hear words like polyfilltranspile, and even ponyfill used. For example, someone might say, “In order to use this in older browsers, you’ll need to use Babel to transpile the code.” Or maybe, “Make sure to provide a polyfill for this functionality so that older browsers can use it.”

If you’re not familiar with these terms, you may be asking yourself, “What’s the difference? Are these all just interchangeable words that mean the same thing?”

In this article, we’ll define these terms and clear the air of any surrounding confusion.

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Polyfills, Ponyfills, and Transpiling

Polyfills, Ponyfills, and Transpiling

When discussing new JavaScript features and syntax, it’s common to hear words like polyfilltranspile, and even ponyfill used. For example, someone might say, “In order to use this in older browsers, you’ll need to use Babel to transpile the code.” Or maybe, “Make sure to provide a polyfill for this functionality so that older browsers can use it.”

If you’re not familiar with these terms, you may be asking yourself, “What’s the difference? Are these all just interchangeable words that mean the same thing?”

In this article, we’ll define these terms and clear the air of any surrounding confusion.

#javascript

Transpilers and Polyfills in JavaScript

In JavaScript, a new proposal to the language is often analyzed if worth appearing on the list of the ECMA262 GitHub page (https://github.com/tc39/ecma262) before progressing to the specification (http://www.ecma-international.org/publications/standards/Ecma-262.htm).

Drafted proposals already in the specification are approved only if they are interesting and easy to learn. Successive proposals are then incorporated into the JavaScript engine.

The side effect is that older engines are unable to implement such codes.

In this tutorial, you will learn how to translate or transform (transpile) modern code to work on older engines.

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What is the difference between Polyfilling and Transpiling?

Today, a new developer who has started working with us has asked me what a Polyfill is and if it is the same as transpile the code, so to respond to this, I have encouraged myself to write this little article.

Some of the newest features sometimes aren’t available in all browsers. So, how can I use all these new features? Do I have to expect until they are implemented? And, what happens with old browsers?

The answer is NO. There are two main methods you can use to enable the newer JavaScript features in your browser: Polyfilling and Transpiling.

Polyfilling

The term “polyfill” is used to refer to taking the definition of a feature and provide an equivalent piece of code to give modern functionality on older browsers that do not natively support it.

For example, consider the following utility: Number.isNaN.

ES6 defines this utility to provide a better check than the original for NaN values. Still, if your browser does not support it (rare nowadays), you can easily create a polyfill for this utility and start using it regardless of whether your browser supports it or not.

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Difference Between Transpiler & Polyfills

In this tutorial, we are going to learn the difference between Transpiler & Polyfills  in Javascript

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Polyfill: PHP Polyfills

Symfony Polyfill

This project backports features found in the latest PHP versions and provides compatibility layers for some extensions and functions. It is intended to be used when portability across PHP versions and extensions is desired.

Polyfills are provided for:

  • the apcu extension when the legacy apc extension is installed;
  • the ctype extension when PHP is compiled without ctype;
  • the mbstring and iconv extensions;
  • the uuid extension;
  • the MessageFormatter class and the msgfmt_format_message functions;
  • the Normalizer class and the grapheme_* functions;
  • the utf8_encode and utf8_decode functions from the xml extension or PHP-7.2 core;
  • the Collator, NumberFormatter, Locale and IntlDateFormatter classes, limited to the "en" locale;
  • the intl_error_name, intl_get_error_code, intl_get_error_message and intl_is_failure functions;
  • the idn_to_ascii and idn_to_utf8 functions;
  • the hex2bin function, the CallbackFilterIterator, RecursiveCallbackFilterIterator and SessionHandlerInterface classes introduced in PHP 5.4;
  • the array_column, boolval, json_last_error_msg and hash_pbkdf2 functions introduced in PHP 5.5;
  • the password_hash and password_* related functions introduced in PHP 5.5, provided by the ircmaxell/password-compat package;
  • the hash_equals and ldap_escape functions introduced in PHP 5.6;
  • the *Error classes, the error_clear_last, preg_replace_callback_array and intdiv functions introduced in PHP 7.0;
  • the random_bytes and random_int functions introduced in PHP 7.0, provided by the paragonie/random_compat package;
  • the PHP_INT_MIN constant introduced in PHP 7.0,
  • the SessionUpdateTimestampHandlerInterface interface introduced in PHP 7.0,
  • the is_iterable function introduced in PHP 7.1;
  • a Binary utility class to be used when compatibility with mbstring.func_overload is required;
  • the spl_object_id and stream_isatty functions introduced in PHP 7.2;
  • the mb_ord, mb_chr and mb_scrub functions introduced in PHP 7.2 from the mbstring extension
  • the sapi_windows_vt100_support function (Windows only) introduced in PHP 7.2;
  • the PHP_FLOAT_* constant introduced in PHP 7.2;
  • the PHP_OS_FAMILY constant introduced in PHP 7.2;
  • the is_countable function introduced in PHP 7.3;
  • the array_key_first and array_key_last functions introduced in PHP 7.3;
  • the hrtime function introduced in PHP 7.3;
  • the JsonException class introduced in PHP 7.3;
  • the get_mangled_object_vars, mb_str_split and password_algos functions introduced in PHP 7.4;
  • the fdiv function introduced in PHP 8.0;
  • the get_debug_type function introduced in PHP 8.0;
  • the preg_last_error_msg function introduced in PHP 8.0;
  • the str_contains function introduced in PHP 8.0;
  • the str_starts_with and str_ends_with functions introduced in PHP 8.0;
  • the ValueError class introduced in PHP 8.0;
  • the UnhandledMatchError class introduced in PHP 8.0;
  • the FILTER_VALIDATE_BOOL constant introduced in PHP 8.0;
  • the get_resource_id function introduced in PHP 8.0;
  • the Attribute class introduced in PHP 8.0;
  • the Stringable interface introduced in PHP 8.0;
  • the PhpToken class introduced in PHP 8.0 when the tokenizer extension is enabled;
  • the array_is_list function introduced in PHP 8.1;
  • the enum_exists function introduced in PHP 8.1;
  • the MYSQLI_REFRESH_REPLICA constant introduced in PHP 8.1;
  • the ReturnTypeWillChange attribute introduced in PHP 8.1;
  • the AllowDynamicProperties attribute introduced in PHP 8.2;
  • the SensitiveParameter attribute introduced in PHP 8.2;
  • the SensitiveParameterValue class introduced in PHP 8.2;

It is strongly recommended to upgrade your PHP version and/or install the missing extensions whenever possible. This polyfill should be used only when there is no better choice or when portability is a requirement.

Compatibility notes

To write portable code between PHP5 and PHP7, some care must be taken:

  • \*Error exceptions must be caught before \Exception;
  • after calling error_clear_last(), the result of $e = error_get_last() must be verified using isset($e['message'][0]) instead of null !== $e.

Usage

When using Composer to manage your dependencies, you should not require the symfony/polyfill package, but the standalone ones:

  • symfony/polyfill-apcu for using the apcu_* functions,
  • symfony/polyfill-ctype for using the ctype functions,
  • symfony/polyfill-php54 for using the PHP 5.4 functions,
  • symfony/polyfill-php55 for using the PHP 5.5 functions,
  • symfony/polyfill-php56 for using the PHP 5.6 functions,
  • symfony/polyfill-php70 for using the PHP 7.0 functions,
  • symfony/polyfill-php71 for using the PHP 7.1 functions,
  • symfony/polyfill-php72 for using the PHP 7.2 functions,
  • symfony/polyfill-php73 for using the PHP 7.3 functions,
  • symfony/polyfill-php74 for using the PHP 7.4 functions,
  • symfony/polyfill-php80 for using the PHP 8.0 functions,
  • symfony/polyfill-php81 for using the PHP 8.1 functions,
  • symfony/polyfill-php82 for using the PHP 8.2 functions,
  • symfony/polyfill-iconv for using the iconv functions,
  • symfony/polyfill-intl-grapheme for using the grapheme_* functions,
  • symfony/polyfill-intl-idn for using the idn_to_ascii and idn_to_utf8 functions,
  • symfony/polyfill-intl-icu for using the intl functions and classes,
  • symfony/polyfill-intl-messageformatter for using the intl messageformatter,
  • symfony/polyfill-intl-normalizer for using the intl normalizer,
  • symfony/polyfill-mbstring for using the mbstring functions,
  • symfony/polyfill-util for using the polyfill utility helpers.
  • symfony/polyfill-uuid for using the uuid_* functions,

Requiring symfony/polyfill directly would prevent Composer from sharing correctly polyfills in dependency graphs. As such, it would likely install more code than required.

Design

This package is designed for low overhead and high quality polyfilling.

It adds only a few lightweight require statements to the bootstrap process to support all polyfills. Implementations are then loaded on-demand when needed during code execution.

If your project requires a minimum PHP version it is advisable to add polyfills for lower PHP versions to the replace section of your composer.json. This removes any overhead from these polyfills as they are no longer part of your project. The same can be done for polyfills for extensions that you require.

If your project requires php 7.0, and needs the mb extension, the replace section would look something like this:

{
    "replace": {
        "symfony/polyfill-php54": "*",
        "symfony/polyfill-php55": "*",
        "symfony/polyfill-php56": "*",
        "symfony/polyfill-php70": "*",
        "symfony/polyfill-mbstring": "*"
    }
}

Polyfills are unit-tested alongside their native implementation so that feature and behavior parity can be proven and enforced in the long run.

Download Details:

Author: Symfony
Source Code: https://github.com/symfony/polyfill 
License: MIT license

#php #symfony #component