JavaScript是一种广泛使用的编程语言，它有一些被保留的关键字，这些关键字不能用作变量名或参数名。这些关键字在代码中起着非常重要的作用，因此开发人员在编写代码时需要避免使用它们。

下面是 JavaScript 中的一些常见保留字：

abstract  boolean  break  byte  case  catch  char  class  const  continue
debugger  default  delete  do  double  else  enum  export  extends  false
final  finally  float  for  function  goto  if  implements  import  in
instanceof  int  interface  long  native  new  null  package  private  protected
public  return  short  static  super  switch  synchronized  this  throw  throws
transient  true  try  typeof  var  void  volatile  while  with  yield

我们可以使用下面的代码来检查我们的变量名是否是 JavaScript 中的保留字：

function checkReservedWord(variableName){
return JavascriptReservedWords.indexOf(variableName) !== -1;
}
const JavascriptReservedWords = [
"abstract","await",
"boolean","break","byte",
"case","catch","char",
"class","const","continue",
"debugger","default","delete",
"do","double","else",
"enum","export","extends",
"false","final","finally",
"float","for","function",
"if","implements","import",
"in","instanceof","int",
"interface","let","long",
"native","new","null",
"package","private","protected",
"public","return","short",
"static","super","switch",
"synchronized","this","throw",
"throws","transient","true",
"try","typeof","var",
"void","volatile","while",
"with","yield"
 ];

除了以上保留字，有些保留字只在严格模式下才会生效：

arguments  eval

在严格模式下，不能为函数实参指定arguments名称，否则会抛出语法错误异常。eval也有一些限制，不能用作变量名或参数名。

总之，在编写代码时，确保不要使用 JavaScript 中的保留字作为变量名或参数名是非常重要的。否则，代码将无法工作或会导致不可预测的结果。