Returns the position of the first occurrence of a substring.
Required. A String object or string literal.
Required. The substring to search for in the string
Optional. The index at which to begin searching the String object. If omitted, search starts at the beginning of the string.
The indexOf method returns the beginning of the substring in the String object. If the substring is not found, -1 is returned.
If startindex is negative, startindex is treated as zero. If it is greater than the highest index, it is treated as the highest 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.
Supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards, Internet Explorer 10 standards, Internet Explorer 11 standards. Also supported in Store apps (Windows 8 and Windows Phone 8.1). See Version Information.