Just wrap it inside an extra pair of curly braces.
$js = <<<EOS
var data = {{$jsObjectData}};
EOS;
Question
$js = <<<EOS
var data = {$jsObjectData};
EOS;
results in var data = ~some object data~
Escaping the brace:
$js = <<<EOS
var data = \{$jsObjectData};
EOS;
results in var data = \{~some object data~}
I can't understand why does that backslash leak through it.
Desired output: var data = {~some object data~}
Solution
Just wrap it inside an extra pair of curly braces.
$js = <<<EOS
var data = {{$jsObjectData}};
EOS;