JS to determine if the field is empty IsNull

When the IF condition is null/undefined/0/nan/"" Expression in JS, all are interpreted as false, and all are also true.
Null-judging function
function IsNull (arg1)
{
return!arg1 && arg1!==0 &&typeof arg1!== "boolean"? True:false;
}

Alert (IsNull (null)); True
Alert (IsNull (")); True
Alert (IsNull ()); True
varaa={};
Alert (IsNull (AA.A)); True
Alert (isNull (0)); False
Alert (IsNull (' 0 ')); False
Alert (IsNull (true)); False
Alert (IsNull ("undefined")); False
Alert (isNull (undefined)); True
Alert (IsNull ([])); False
Alert (IsNull ({})); False

From: http://blog.sina.com.cn/s/blog_68ead6830101cx3u.html