Why is javascript the only client side scripting language implemented in browsers?
Why don't browsers add support for, say, Python scripting as an alternative to Javascript? Or more general purpose scripting languages? Is there a reason that Javascript is the only one implemented across browsers? After all, the script tag does have support to specify the scripting language used.

(I know there is VBScript support in IE.)
Why is javascript the only client side scripting language implemented in browsers?
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Why don't browsers add support for, say, Python scripting as an alternative to Javascript? Or more general purpose scripting languages? Is there a reason that Javascript is the only one implemented across browsers? After all, the script tag does have support to specify the scripting language used.

(I know there is VBScript support in IE.)