js判斷中文字元串長度和js截取中文字元串

//獲取字元串長度
String.prototype.strLen = function() {  
    var len = 0;  
    for (var i = 0; i < this.length; i++) {  
        if (this.charCodeAt(i) > 255 || this.charCodeAt(i) < 0) len += 2; else len ++;  
    }  
    return len;  
}  
//將字元串拆成字元，並存到數組中  
String.prototype.strToChars = function(){  
    var chars = new Array();  
    for (var i = 0; i < this.length; i++){  
        chars[i] = [this.substr(i, 1), this.isCHS(i)];  
    }  
    String.prototype.charsArray = chars;  
    return chars;  
}  
//判斷某個字元是否是漢字  
String.prototype.isCHS = function(i){  
    if (this.charCodeAt(i) > 255 || this.charCodeAt(i) < 0)   
        return true;  
    else  
        return false;  
}  
//截取字元串（從start位元組到end位元組）  
String.prototype.subCHString = function(start, end){  
    var len = 0;  
    var str = "";  
    this.strToChars();  
    for (var i = 0; i < this.length; i++) {  
        if(this.charsArray[i][1])  
            len += 2;  
        else  
            len++;  
        if (end < len)  
            return str;  
        else if (start < len)  
            str += this.charsArray[i][0];  
    }  
    return str;  
}  
//截取字元串（從start位元組截取length個位元組）  
String.prototype.subCHStr = function(start, length){  
    return this.subCHString(start, start + length);  
}


轉：http://blog.csdn.net/clh604/article/details/8278303