字符串操作

var str = ‘absdfdfsdfsdf‘;
function aa(str){
    var obj = {}, key = 0;
    for(var i=0; i<str.length; i++){
        key = str.charAt(i);
        if(obj[key]){
            obj[key]++;
        }else{
            obj[key] = 1;
        }
    }
    var m = 0, i = 0;
    for(var key in obj){
        if(obj[key] > m){
            m = obj[key];
            i = key;
        }
    }
    console.log(i , m)
}

var str = "abcdefg";
var idx = str.indexOf("efg");

var efg = str.substr(str.indexOf("efg"), 3); 
alert(efg);