JS delete the last character of the string

var str = "abc,def,ghi,";

1.substr() Method to extract from a string start The specified number of characters from which the subscript begins .

str = str.substr(0, str.length - 1);  

2.substring() Method is used to extract characters that are mediated between two specified subscripts .

str = str.substring(0, str.length - 1);

3.lastIndexOf() Method returns the last occurrence of a specified string value , Search from back to front in a specified position in a string

str = str.substring(0, str.lastIndexOf(','));