SOURCE

document.write("3月14日"+"<br/>");
document.write("------------------------------<br/>"); 

document.write("---case---<br/>"); 
var welcomestring = "welcome";
document.write("字符串长度："+welcomestring.length + "<br/>");
document.write("原："+welcomestring + "<br/>");
document.write("所有字符变成小写："+welcomestring.toLowerCase() + "<br/>");
document.write("所有字符变成大写："+welcomestring.toUpperCase() + "<br/>");


document.write("3月15日"+"<br/>");
function writeDocument(variable) {
    document.write(variable + "<br/>");
} 
//获取某一个字符  语法： 字符串名.charAt()
writeDocument("//------charAt-------");
writeDocument(welcomestring.charAt(2));
writeDocument(welcomestring.charAt(6));

//截取字符串
writeDocument("//------substring-------");
writeDocument(welcomestring.substring(3));
writeDocument(welcomestring.substring(0,2));

//替换字符串
writeDocument("//------replace-------");
var sentence = "We have fun in our class. Do you have fun in your class?";
writeDocument(sentence);
writeDocument(sentence.replace("class","programming calss"));
writeDocument(sentence.replace(/class/g,"programming class"));

//分割字符串
writeDocument("");
writeDocument("//------spit-------");
writeDocument(sentence.split(" ")); //按空格分割
writeDocument(sentence.split(""));  //按字符串分割
writeDocument(sentence.split(",")); //按逗号分割

//检索字符串位置
writeDocument("");
writeDocument("//------indexOf/lastIndexOf/match/search-------");
writeDocument(sentence.indexOf("class")); //首先出现的下标位置
writeDocument(sentence.lastIndexOf("class"));  //最后出现的下标位置
writeDocument(sentence.match("class")); //搜索
writeDocument(sentence.match(/class/g)); //搜索所以
writeDocument(sentence.search(/class/g));  //找到第一个出现的位置

/*writeDocument("");
function countChar(stringToCount,char){
    var charCount = 0;
    var i = 0;
    for(i=0;i<stringToCount.length;i++){

    }
    return charCount;
}
var stringToCount = "Can you can a can as a Canner can can a can";
writeDocument("There are " + countChar(stringToCount, "c") + " c in " + stringToCount()); 
*/

writeDocument("//------indexOf/lastIndexOf/match/search-------");
function countChar(stringToCount, char) {
    var charCount = 0;
    for(var i=0;i<stringToCount.length;i++){
        var a = stringToCount.charAt(i);
        //将每一个字符切换成小写，然后判断是否与 c 相等
        if(a.toLowerCase() == "c"){
            charCount+=1;
        }
    }
    return charCount;
}
var stringToCount = "Can you can a can as a Canner can can a can";
writeDocument("There are " + countChar(stringToCount, "c") + " c in " + stringToCount);


//统计字符串中数字的个数
writeDocument("//------统计字符串中数字的个数-------");
function countNumber(stringtoCount) {

    var numCount = 0;

    //实现你的逻辑
    for (var i = 0; i < stringtoCount.length; i++) {
        //var char = stringtoCount.charAt(i);
        //isNaN()对空格字符会转化为0，需要加个判断charAt(i)不能为空格
        if (!isNaN(stringtoCount.charAt(i)) && stringtoCount.charAt(i) != " ") {
            ++numCount;
        }
    }
    return numCount;
 //   countNumber("12w36jkgsg");
    //writeDocument(countNumber("12w36jkgsg"));
}
writeDocument(countNumber("12w36jkgsg"));