Is JavaScript case-sensitive?

Yes.  When you define an identifier in JavaScript, the name of the identifier is case-sensitive.  For example, if you define:

<meta name=IS_Action_foo>

then you must call it using

IS_Action_foo.click();

Likewise, if you define:

<meta name=IS_Action_FoO>

then you must call it using:

IS_Action_FoO.click();