为什么新的Function()在参数中返回注释/**/？

Question

在chrome 47和nodejs v0.12中

new Function('myArg','return "my function body";')

给出以下结果:

function anonymous(myArg /**/) {
  return "my function body"
}

为什么函数参数中有注释/**/？

Answer 1

如下面的Chromium问题所示,这是一种解决方法,可以修复涉及不平衡块注释的边缘情况.如V8源代码中所述:

function NewFunctionString(arguments, function_token) {
  var n = arguments.length;
  var p = '';
  if (n > 1) {
    p = ToString(arguments[0]);
    for (var i = 1; i < n - 1; i++) {
      p += ',' + ToString(arguments[i]);
    }
    // If the formal parameters string include ) - an illegal
    // character - it may make the combined function expression
    // compile. We avoid this problem by checking for this early on.
    if (%_CallFunction(p, ')', StringIndexOfJS) != -1) {
      throw MakeSyntaxError('paren_in_arg_string', []);
    }
    // If the formal parameters include an unbalanced block comment, the
    // function must be rejected. Since JavaScript does not allow nested
    // comments we can include a trailing block comment to catch this.
    p += '\n/' + '**/';
  }
  var body = (n > 0) ? ToString(arguments[n - 1]) : '';
  return '(' + function_token + '(' + p + ') {\n' + body + '\n})';
}

Answer 2

这最初被添加到捕获如下的情况并抛出错误:

Function("/*", "*/){alert('bad');")

这应该会导致语法错误,但在添加附加内容之前/**/,它将被转换为:

function anonymous(/*) {
  */){alert('bad');
}

这相当于

function anonymous(/*...*/) {
  alert('bad');
}

因此没有语法错误.更改后,额外的评论现在变为:

function anonymous(/*/**/) {
  */){alert('bad');
}

这正确地给出了语法错误:

Uncaught SyntaxError: Unexpected token *(…)

源修订和原始错误报告.