JavaScript Array method: indexOf()
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The indexOf() method (when applied to a JavaScript
array) returns
the index of the first element of an array found when an array is searched.
It
has the following syntax with the following parameters. It returns a number
as above (or -1 if no array element passes the test).
array.indexOf(item, start)
Parameter
|
Required / Optional
|
Description
|
item
|
Required
|
Item to search for
|
start
|
Optional
|
Index value at which to
start search. Negative values indicate start from a position counting back
from the end and then search to the end
|
EXAMPLE:
HTML USED IN THIS EXAMPLE:
<!DOCTYPE html>
<html> <!-- Copyright (c) Nematrian Limited 2018 -->
<head>
<style>
table,th,tr,td {border: 1px solid black; border-collapse: collapse;}
</style>
</head>
<body>
<table>
<tr>
<th>Example</th>
<th>Resulting value of <code>x</code></th>
</tr>
<tr>
<td><code id="Example"></code></td>
<td><code id="Result"></code></td>
</tr>
</table>
<script>
var h = ["a","b","b"];
document.getElementById("Example").innerHTML =
'var h = ["a","b","b"];<br>' +
'var x = h.indexOf("b");';
document.getElementById("Result").innerHTML = h.indexOf("b");
</script>
</body>
</html>
|
FUNCTION THAT MAY ASSIST IN TESTING WHETHER FEATURE IS SUPPORTED:
function isSupportedJavaScriptMethodArrayIndexOf() {
var h = [1, 2, 3]; return !!h.indexOf;
} |
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