JS delete the last bit of the string

1.substr() Method

var str = "abc,def,ghi,";
str = str.substr(0, str.length - 1);
console.log(str) //  return abc,def,ghi

2.substring() Method

var str = "abc,def,ghi,";
str = str.substring(0, str.length - 1);
console.log(str) //  return abc,def,ghi

3.lastIndexOf() Method

var str = "abc,def,ghi,";
str = str.substring(0, str.lastIndexOf(','));
console.log(str) //  return abc,def,ghi