javascript中字符串处理，常用的方法汇总

var string = "to be or not to be";
      
var res = string.length
var res = string[-1]
console.log(res)

var string = "to be or not to be";
var res = string.charAt(3)
console.log(res)

var res = string.trim()
console.log(string)
console.log(res)

/*找不到返回-1*/
var string = "to be or not to be";
var res = string.indexOf("z")
console.log(res)

/*找不到返回-1*/
var res = string.lastIndexOf("zzz")
console.log(res);

var res = string.concat("d:\\","python32\\","day42");
console.log(res);

/* string.slice(开始值,结束值) 字符串的切片  留头舍尾  [支持逆向下标]*/
var string = "11122233e or not to be";
var res = string.slice(1,7);
var res = string.slice(-5,-1);      // to b
// var res = string.slice(-5,-10); //截取不到返回空
console.log(res,"<==1==>")

/* string.substr(开始值,截取几个) */
var string = "11122233e or not to be";
var res = string.substr(3,4)
console.log(res,"<==2==>")

var string = "11122233e or not to be";
var res = string.split(" ")
console.log(res,"<==3==>")

var string = "11122233e Or noT tO be";
res = string.toUpperCase();
res = string.toLowerCase();
console.log(res,"<==4==>")

var string = "aaabbb oldaoy ccc"
var res = string.search(/oldboy/)
console.log(res,"<==5==>")

/* /正则表达式/修饰符 g:全局匹配 i:不区分大小写 m:多行匹配  */
var string = "我的电话是 : 13838384388 你的电话是: 13854381438"
var res = string.match(/\d{11}/);  // 匹配一个
var res = string.match(/\d{11}/g); // 匹配多个,(需要修饰符加上g)
console.log(res)
console.log(res[0])
console.log(res[1])

/* replace默认只替换一次 */
var string = "to be or not to be";
var res = string.replace("to","two")
console.log(res,"<==6==>")    

function myreplace(string,a,b){
    /*
        找最后一个to,如果找不到返回-1
        如果能找到就不停的进行替换,直到-1为止,循环终止;
    */
    while(string.lastIndexOf(a) != -1){
        console.log(1)
        string = string.replace(a,b);
    }
    return string;
}     
var string = "to be or not to be";   
var res = myreplace(string,"to","two")
console.log(res) // two be or not two be

var string = "to be or not to be";
var res = string.replace(/to/g,"two");
console.log(res)