SOURCE

function writeDocument(variable) {
    document.write(variable + "<br/>");
} 


var welcomeString ="welcome";

document.write(welcomeString+"<br/>");
//字符串长度
document.write(welcomeString.length+"<br/>");
writeDocument("//case---------------------------------");
document.write(welcomeString.toLowerCase()+"<br/>");
//小写字母转换为大写字母（大小写转换）
document.write(welcomeString.toUpperCase()+"<br/>");
writeDocument("//charAt---------------------------------");

writeDocument(welcomeString.charAt(2));
writeDocument(welcomeString.charAt(6));
writeDocument("//substring---------------------------------");
writeDocument(welcomeString.substring(3));
writeDocument(welcomeString.substring(0,2));
writeDocument("//replace---------------------------------");
//替换字符串
var sentence="We have fun in our class. Do you have fun in your class";
writeDocument(sentence);
//writeDocument(sentence.replace("We","You"));
writeDocument(sentence.replace("class","programing class"));
writeDocument(sentence.replace(/class/g,"programing class"));
writeDocument("//split---------------------------------");
//分割字符串
var splitaSentence = "We have fun in our class";
writeDocument(splitaSentence);
writeDocument(splitaSentence.split(" "));

writeDocument(welcomeString);
writeDocument(welcomeString.split(""));

writeDocument(sentence);
writeDocument(sentence.split(""));
writeDocument("//IndexOf---------------------------------");
//检索字符串的位置（获取指定位置字符）
//第一个出现class的位置
writeDocument(sentence.indexOf("class"));
//最后一个出现class的位置
writeDocument(sentence.lastIndexOf("class"));

writeDocument(sentence.match("class"));
writeDocument(sentence.match(/class/g));
writeDocument(sentence.search(/class/g));

writeDocument("//IndexOf---------------------------------");

//判断一个字符串里有多少个字母c（指定字符的统计）
function countChar(stringValue,char){
    var charCount = 0;

    for (var i=0;i<stringValue.length;++i){
        if(stringValue.charAt(i).toLowerCase()==char){
            ++charCount;
        }
    }
    return charCount;
}
var stringValue="Can you can a can as a Canner can can a can";
writeDocument("There are"+countChar(stringValue,"c")+"'c' in sentence.");
writeDocument("//countNumber---------------------------------");

//统计字符串中数字的个数
function countNumber(stringtoCount) 
{
    var numCount = 0;
        for (var i = 0; i < stringtoCount.length; i++)
        {            
            var char = stringtoCount.charAt(i);
            //isNaN()对空格字符会转化为0
            if (char != " " && !isNaN(char))
            {
                numCount++;
            }
        }
        return numCount;
}
document.write(countNumber("37ggih4kjg9 hj7"));
/*function countChar(str, char) {
    var count = 0;
    var str="Can you can you cn";
    var char = str.charAt(char);
    if (char.toLowerCase() == "c") {
        count += 1;
    }
    document.write("字符串中含有" + count + "个字母c");
    return count;
} 
countChar();*/