Sunday, December 13, 2009

String functions in JavaScript


Most common string functions in JavaScript




Sometimes you need to deal with strings in javascript. It will be getting a length of a string or determine the character position in a string.




How to get a length of a string in java script?


Use the length method to find out how many characters in string. It returns the total characters in the string.

How Change the case of a string?


You can change the case of a string to lowercase or to upper case using javascript function.
To change a string to lowercase use toLowerCase() function and make uppercase use toUpperCase() function.

How to get the index of a character?


You can get the index of the first occurrence of a specified character using indexOf() function.
This returns -1 if the character not present in the given string, otherwise it returns the index of the first occurrence. The index starts from zero. There is an another method called lastIndexOf() to get the index of a specified character. It start checking right to left.

How create sub string in javascript?


Use substr() function to make sub strings in javascript. This method returns specified parts of the string. You have to
specify the starting position of the string and then how many characters do you want to extract from the string. Take into mind first character is 0. If ending position is greater than the total length of the string it returns the whole input string as result. Use substring() function to get all characters between starting and ending positions.





Demo- String functions in JavaScript.
1. Get string length using JavaScript.
Enter string to get length


view code

2.Change text case using JavaScript.
Enter string to change the case



view code




3.Get the index of a character using JavaScript.




 Enter a character



Type your text


view code

4.Make sub strings using JavaScript.

Enter a string to make sub string



Starting position



 Enter ending position


view code



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1. Example code for get string length using JavaScript.

JavaScript Code
<script type="text/javascript" language="javascript">

<!--

function getStringLength(str){

if(str==''){

alert("Please enter a string");

}else{

alert(str.length+" characters in the string");

}

return true;

}

-->

</script>
Html Code


<html>

 <head>

  <title>Get string length in JavaScript </title>

 </head>

<body>

 <input type="text" id="stringLength" name="stringLength" />
<input name="getStringLength" type="button" onClick="javascript:getStringLength(this.value);" value="Get Length" />

</body>

</html>

2. Sample code for change text case in JavaScript.

JavaScript code
<script type="text/javascript" language="javascript">

<!--

function changeCase(textCase){

var text=document.getElementById("txtUpperorLower").value;

if(text==''){

alert("Please enter a string");

return false;

}

switch(textCase){

case 1:{

alert(text.toUpperCase());

}break;

case 2:{

alert(text.toLowerCase());

}break;

}

return true;

}
-->

</script>

<html>

 <head>

  <title>Chanage text case in JavaScript </title>

 </head>

<body>

 <input type="text" name="txtUpperorLower" id="txtUpperorLower" value="" />

<input name="setUpperCase" id="setUpperCase" type="button" onClick="javascript:changeCase(1);" value="To Upper" /> <input name="setLowerCase" id="setLowerCase" type="button" onClick="javascript:changeCase(2);" value="To Lower" />

</body>

</html>

3. Sample code for get character index in JavaScript.

JavaScript code
<script type="text/javascript" language="javascript">

<!--

function getIndex(){

var text=document.getElementById("txtGetIndex").value;

var textChar=document.getElementById("txtCharacter").value;

if(text==''){

alert("Please enter a string");

return false;

}else if(textChar==''){

alert("Please enter a character");

return false;

}else if(textChar.length>1){

alert("Please enter a single character");

return false;

}

var index=text.indexOf(textChar)

if(index<0){

alert("Character not found");

}else{

alert("Index of "+textChar+" is "+index);

}

return true;

} -->


</script><html>

 <head>

  <title>Get character index in JavaScript </title>

 </head>

<body>

 Enter a character <input type="text" name="txtCharacter" id="txtCharacter" value="" size="5" /> Type your text

<input type="text" name="txtGetIndex" id="txtGetIndex" value="" />

<input name="setCharacterIndex" id="setCharacterIndex" type="button" onClick="javascript:getIndex();" value="Get Index" />

</body>

</html>

4. Sample code for making sub string using JavaScript.

JavaScript code
<script type="text/javascript" language="javascript">

<!--

function getSubstring(){

var start=document.getElementById("txtStart").value;

var end =document.getElementById("txtEnd").value;

var text=document.getElementById("txtToSubstring").value;

if(isNaN(start)){

alert("Please enter a valid start value");

return false;

}else if(isNaN(end)){

alert("Please enter a valid ending value");

return false;

}else if(start<0 || end<0 || end==0){

alert("Please enter a valid start and ending value");

return false;

}else if(text==''){

alert("Please enter a string to make substring");

return false;

}



alert(text.substr(start,end));

return true;

}-->


</script><html>

 <head>

  <title>Make substring in JavaScript </title>

 </head>

<body>

Enter a string to make substring <input type="text" name="txtToSubstring" id="txtToSubstring" value="Hello World" /><br />

Starting position <input type="text" name="txtStart" id="txtStart" value="0" size="5" /><br />

Enter ending position <input type="text" name="txtEnd" id="txtEnd" value="2" size="5" />

<input name="getSubstring" id="getSubstring" type="button" onClick="javascript:getSubstring();" value="Make Substring" />

</body>

</html>


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©-Copyright By Duminda Chamara
JavaScript Validation  

1 comments:

Đẩu Anh said...

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