indexOf()練習，查找某個字符出現的次數

<script type="text/javascript">	
	
	var myString='abcadaefaaghai';
	var position=0;
	var count=0;
	
	while(position!=-1){
		position=myString.indexOf('a',position);
		
		if(position!=-1){
			count++;
			position++;
		}
	}
	
	alert(count);
</script>