JavaScript eval

Question

Why doesn't this eval call alert("Summer") ?

eval('(caption="Summer";alert(caption))');

Does it have something to do with the quotes in "Summer"?

Answer 1

Uncaught SyntaxError: Unexpected token ;

The outer parentheses make no syntactical sense. Try this:

eval('caption="Summer";alert(caption)');

Answer 2

Chrome console:

eval('(caption="Summer";alert(caption))')
SyntaxError: Unexpected token ;

This works:

eval('caption="Summer"; alert(caption)')

Answer 3

额外的括号错了，这是正确的：

eval('caption="Summer";alert(caption)');

Answer 4

更好的方法是执行此操作并避免语法问题，请执行以下操作，

eval(function(){var x="test"; alert(x)}());