Returns the character position where the first occurrence of a substring occurs within a String object.
Required. A String object or literal.
Required. Substring to search for within the String object.
Optional. Integer value specifying the index to begin searching within the String object. If omitted, searching starts at the beginning of the string.
The indexOf method returns an integer value indicating the beginning of the substring within the String object. If the substring is not found, a -1 is returned.
If startindex is negative, startindex is treated as zero. If it is larger than the greatest character position index, it is treated as the largest possible index.
Searching is performed from left to right. Otherwise, this method is identical to lastIndexOf.
The following example illustrates the use of the indexOf method.
var str1 = "BABEBIBOBUBABEBIBOBU"
var s = str1.indexOf(str2);