The programs in this language are called scripts. They can be written right in a web page’s HTML
and run automatically as the page loads.
Scripts are provided and executed as plain text. They don’t need special preparation or
compilation to run.
popular at that time, so it was decided that positioning a new language as a “younger brother”
of Java would help.
called ECMAScript , and now it has no relation to Java at all.
Different engines have different “codenames”. For example:
V8 – in Chrome and Opera.
SpiderMonkey – in Firefox.
…There are other codenames like “Trident” and “Chakra” for different versions of IE,
“ChakraCore” for Microsoft Edge, “Nitro” and “SquirrelFish” for Safari, etc.
The terms above are good to remember because they are used in developer articles on the
internet. We’ll use them too. For instance, if “a feature X is supported by V8”, then it probably
works in Chrome and Opera
different domain, protocol or port).
This is called the “Same Origin Policy”. To work around that, both pages must agree for data
This limitation is, again, for the user’s safety. A page from http://anysite.com which a
user has opened must not be able to access another browser tab with the URL
http://gmail.com and steal information from there.
from. But its ability to receive data from other sites/domains is crippled. Though possible, it
requires explicit agreement (expressed in HTTP headers) from the remote side. Once again,
that’s a safety limitation.
Modern browsers also allow plugin/extensions which may ask for extended permissions.
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