In Javascript you will often need to find the position of a certain character in a string. You will learn this by reading this easy tutorial.
Consider the following Javascript functions:
| JavaScript Code |
|---|
stringObject.indexOf(searchvalue,fromindex); stringObject.lastIndexOf(searchvalue,fromindex); |
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The indexOf method returns the position of the first occurrence of the specified value searchvalue in the stringObject string. The lastIndexOf() method returns the position of the last occurrence of the searchvalue, but is searching backwards from the specified position.
We will create a demo to understand how this works. The following HTML creates two textboxes, one for the string to search in, and one for the character of string to be searched, and a button that displays in an alert box the position of the searched string.
| HTML Code |
|---|
<html>
<head>
<title>How the javascript indexOf() method works</title>
</head>
<body>
<input type="text" id="string" />
<input type="text" id="char" />
<input type="submit" value="Get position!" onclick="findPos('string','char')" />
</body>
</html>
|
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Here is the function that returns the position of the character of string specified in the searchString textfield.
| JavaScript Code |
|---|
function findPos(searchIn, searchFor)
{
var string = document.getElementById(searchIn).value;
var character = document.getElementById(searchFor).value;
var pos = string.indexOf(character);
alert('Position of "'+character+'" in "'+string+'" is: '+pos+'!');
}
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So the function above gets the string and character entered in the text fields above and displays an alert message box with the position of that character in the string. You can also use lastIndexOf instead of indexOf.
| JavaScript + HTML Code |
|---|
<html>
<head>
<title>How the javascript indexOf() method works</title>
<script language="javascript" type="text/javascript">
function findPos(searchIn, searchFor)
{
var string = document.getElementById(searchIn).value;
var character = document.getElementById(searchFor).value;
var pos = string.indexOf(character);
alert('Position of "'+character+'" in "'+string+'" is: '+pos+'!');
}
</script>
</head>
<body>
<input type="text" id="string" />
<input type="text" id="char" />
<input type="submit" value="Get position!" onclick="findPos('string','char')" />
</body>
</html>
|
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