我创建了这个小书签来突出显示页面上的用户名和密码框。我可以更改框的颜色，但如果我尝试更改框中的文本，它就不起作用：
<a href="javascript:void(var boxes= $(':text, :password');var selectionBox = $(':password');selectionBox.val('password');for(var i = 0; i < boxes.length;i++){if(boxes[i] == selectionBox[0]){boxes.eq(i-1).val('login');}})">Password box highlighter</a>
我试过了.text = ''，.value = ''和.val('')。
谢谢。
Wrap the code to execute into a function-call:
<a href="javascript:void(function(){var boxes= $(':text, :password');var selectionBox = $(':password');selectionBox.val('password');for(var i = 0; i < boxes.length;i++){if(boxes[i] == selectionBox[0]){boxes.eq(i-1).val('login');}}}())">Password box highlighter</a>
Explanation: void expects an expression(only 1 expression).
An expression is any valid unit of code that resolves to a value
Your code already breaks with the first var-keyword, because declaring a variable is not an expression.
When you wrap the code into a function-call, the expression is the function-call itself, no matter which code will be executed inside the function.