JavaScript judgment character first appears in string position

Grammar
Stringobject.indexof (Searchvalue,fromindex)

<script type= "text/web Effects" >
var str= "Hello world!"//w lowercase
document.write (Str.indexof ("H") + "<br/>")//0
document.write (Str.indexof ("World") + "<br/>")//-1
document.write (Str.indexof ("World"))//6
</script>

Description
This method retrieves the string stringobject from beginning to end to see if it contains substring searchvalue. The location at which to start retrieving is at the fromindex of the string or at the beginning of the string (no fromindex is specified). If a searchvalue is found, it returns the position of the first occurrence of searchvalue. The character position in the Stringobject is starting at 0.

Example
The following example illustrates the use of the IndexOf method.

function Indexdemo (str2) {
var str1 = "Babebibobubabebibobu"
var s = str1.indexof (STR2);
return (s);
}

Tips and comments
Note: the IndexOf () method is case sensitive!

Note: If the string value to retrieve does not appear, the method returns-1.