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Deprecated: Return type of WP_REST_Request::offsetSet($offset, $value) should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/rest-api/class-wp-rest-request.php on line 992

Deprecated: Return type of WP_REST_Request::offsetUnset($offset) should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/rest-api/class-wp-rest-request.php on line 1003

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Deprecated: Return type of WP_Block_List::rewind() should either be compatible with Iterator::rewind(): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 138

Deprecated: Return type of WP_Block_List::offsetExists($index) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 75

Deprecated: Return type of WP_Block_List::offsetGet($index) should either be compatible with ArrayAccess::offsetGet(mixed $offset): mixed, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 89

Deprecated: Return type of WP_Block_List::offsetSet($index, $value) should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 110

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Deprecated: Creation of dynamic property WPCOM_REST_API_V2_Endpoint_Gutenberg_Available_Extensions::$wpcom_is_site_specific_endpoint is deprecated in /var/www/twodee/blog/wp-content/plugins/jetpack/_inc/lib/core-api/wpcom-endpoints/gutenberg-available-extensions.php on line 20

Deprecated: Creation of dynamic property WPCOM_REST_API_V2_Endpoint_Memberships::$wpcom_is_wpcom_only_endpoint is deprecated in /var/www/twodee/blog/wp-content/plugins/jetpack/_inc/lib/core-api/wpcom-endpoints/memberships.php on line 23

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Deprecated: Creation of dynamic property WPCOM_REST_API_V2_Endpoint_Subscribers::$wpcom_is_wpcom_only_endpoint is deprecated in /var/www/twodee/blog/wp-content/plugins/jetpack/_inc/lib/core-api/wpcom-endpoints/subscribers.php on line 15

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» From * To Javascript

teaching machines

From * To Javascript

November 28, 2018 by . Filed under
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programming languages, public.

Educators must contend with students’ prior knowledge of a subject. Sometimes the prior knowledge is advantageous—but not always. What we “know” may be wrong or incomplete. The same is true with programming languages. When learning a new language, you must contend with the baggage you bring from other languages you know.

Suppose you are C or Java programmer and you see this bit of Javascript code:

function isBetween(lo, hi, x) {
  return
    lo <= x &&
    x <= hi;
}

console.log(isBetween(0, 10, 5));
What output do you expect to see?
Probably you expect to see a boolean. In this case, true. But you are wrong. The output is undefined.

Your C or Java knowledge has conditioned you to mostly ignore whitespace and mentally parse statements using semicolons. But Javascript automatically inserts semicolons for you when interpreting your code. In particular, Section 7.9 of the ECMA specification says this:

When a continue, break, return, or throw token is encountered and a LineTerminator is encountered before the next token, a semicolon is automatically inserted after the continue, break, return, or throw token.

Whoops. I long for the day when we no longer manually format our code with whitespace, but leave it to the editor to apply our styles to the token stream. I still want text, just not spaces, tabs, and linebreaks.