js 의 null, undefined, "", 0 은 false 로 바 꿀 수 있 고 다른 것 은 모두 true 입 니 다.

<script src="Person.js"></script>
<div id="disp"></div>
<script language="JavaScript">
	var unde;
	var toCheckArray=new Array(7);
	toCheckArray[0]=null;
	toCheckArray[1]=unde;
	toCheckArray[2]="";	
	toCheckArray[3]=0;
	
	toCheckArray[4]="a";
	toCheckArray[5]="0";
	toCheckArray[6]=1;
	
	for(var e in toCheckArray){
		console.log("value=" + toCheckArray[e] + "  <-->  " + (toCheckArray[e]?true:false)+"     type=  " + typeof(toCheckArray[e]));
	}
	var output="";
	output+="var unde;</br>";
	output+=	'	toCheckArray[0]=null;	'+'	</br>	'	;
	output+=	'	toCheckArray[1]=unde;	'+'	</br>	'	;
	output+=	'	toCheckArray[2]="";	'+'	</br>	'	;
	output+=	'	toCheckArray[3]=0;	'+'	</br>	'	;
	output+=	'		'+'	</br>	'	;
	output+=	'	toCheckArray[4]="a";	'+'	</br>	'	;
	output+=	'	toCheckArray[5]="0";	'+'	</br>	'	;
	output+=	'	toCheckArray[6]=1;	'+'	</br>	'	;


	alert(output);
	 
	output +="<table border=1>";	
	output +="  <TR>	<TD> </TD>	<TD>       </TD>	<TD>typeof</TD>  </TR>";
	for(var e in toCheckArray){
		
		output +="<tr>";
		output +="<td> toCheckArray[" + e + "]: value=" + toCheckArray[e] + "</td> <td>if(value)==" + (toCheckArray[e]?true:false)+"</td> <td>typeof== " + typeof(toCheckArray[e])+"</td>";
		output +="</tr>";
	}
	output+="</table>";
	
	var divTag = document.getElementById("disp");
	divTag.innerHTML=output;
</script>