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indexOf Method (String) (JavaScript)

Returns the character position where the first occurrence of a substring occurs within a String object.

strObj.indexOf(subString[, startIndex])

strObj

Required. A String object or literal.

subString

Required. Substring to search for within the String object.

startIndex

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 str = "original equipment manufacturer";

var s = "";
s += "equip is at position " + str.indexOf("equip");
s += "<br />";
s += "abc is at position " + str.indexOf("abc");

document.write(s);

// Output:
//   equip is at position 9
//   abc is at position -1

Supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards. See Version Information.

Applies To: String Object (JavaScript)

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