SOURCE

var welcomeString="Welcome";
document.write(welcomeString+"<br/>");
document.write(welcomeString.length+"<br/>");
document.write(welcomeString.toLowerCase()+"<br/>");
document.write(welcomeString.toUpperCase()+"<br/>");
document.write(welcomeString.charAt(2)+"<br/>");//获取第3个字符串
document.write(welcomeString.charAt(6)+"<br/>");
document.write(welcomeString.substring(3)+"<br/>");//截取字符串
document.write(welcomeString.substring(0,2)+"<br/>");

document.write('<br/>---------------------------------<br/>');

var sentence = "We have fun in class.Do you have fun in class?"
document.write(sentence+"<br/>");
document.write(sentence.replace("We","You")+"<br/>");//替换字符串（原字符串）
document.write(sentence.replace(/class/g,"programming class")+"<br/>");//替换字符串（正则表达式）

document.write('<br/>---------------------------------<br/>');

var splitSentence = "We have fun in our class";
document.write(splitSentence+"<br/>");
document.write(splitSentence.split(" ")+"<br/>");//空格切割
document.write(welcomeString+"<br/>");
document.write(welcomeString.split("")+"<br/>");//空字符切割
document.write(sentence.split("")+"<br/>");

document.write('<br/>---------------------------------<br/>');
document.write(sentence.indexOf("class")+"<br/>");
document.write(sentence.lastIndexOf("class")+"<br/>");
document.write(sentence.match(/class/g)+"<br/>");
document.write(sentence.search(/class/g)+"<br/>");

document.write('<br/>---------------------------------<br/>');
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";
document.write("字符串中含有" + countChar(stringValue,"c")+ "个字母c");





document.write('<br/>---------------------------------<br/>');
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，需要加个判断charAt(i)不能为空格
                if (char != " " && !isNaN(char)) {
                    document.write(true);
                   // numCount++;
                }else{
                    document.write(false);
                }
            }

     return numCount;
}
//document.write("字符串中含有" +countNumber("3h4e4g9k8o")+"个数字");