javascript 折半查找字符在数组中的位置(有序列表)

/** 
* 折半查找字符在数组中的位置(有序列表) 
* @param array 被检索的数组 
* @param x 要查找的字符 
* @type int 
* @returns 字符在数组中的位置，没找到返回-1 
*/ function binarySearch(array,x){ 
var lowPoint=1; 
var higPoint=array.length; 
var returnValue=-1; 
var midPoint; 
var found=false; 
while ((lowPoint<=higPoint)&&(!found)){ 
midPoint=Math.ceil((lowPoint+higPoint)/2); 
//console.log(lowPoint+"===="+midPoint+"===="+higPoint); 
if(x>array[midPoint-1]){ 
lowPoint=midPoint+1; 
} 
else if(x<array[midPoint-1]){ 
higPoint= midPoint-1; 
} 
else if(x=array[midPoint-1]){ 
found=true; 
} 
} 
if(found){ 
returnValue=midPoint; 
} 
return returnValue; 
} 
/*var array2=[1,2,3,4,5,6,7,8,9,100,109];*/ 
var array2=['a','b','c','d','e','f','g']; 
console.log(binarySearch(array2,'c'));