String Manipulation

All this knowledge will be of no use to you if you have nothing to do with it. Now here is an opportunity to get manipulative with strings. You can use this to format and valid user entries in forms. But I have not yet taught you how to get values from forms. I will go into detail how to get values from form in the advanced section, but for our purposes let me show you how to do it.

Assuming that there is a form element with the name entry. You can make it with this code.
<form name="frm">
<input type="text" name="entry" value="Life is wonderful. Without it we'd all be dead." size=50>
</form>
This code will create a text box like this.

Now we have the contents of the entry field in the variable 'txt'. Now to manipulate it.

Let us convert it to upper case and to lower case.

Finding its length and a charecter at a specified location.

Notice that I gave 'txt.charAt(3)' when I wanted the fourth character. This is because the string's first element is 0 like the array.

Now to find all characters from the 3rd place to the 6th place

Search for a regular expression and replace it.

var txt = document.frm.entry.value
//Searching
var re = /life\s/gi;
if(txt.match(re)) {
alert(re+" Found.")
} else {
alert(re+" is not found")
}
//Replacing
var encrypted = txt.replace(/(.)(.)(.)(.)(.)(.)(.)/g,"$3$6$7$1$2$4$5")
var decrypted = encrypted.replace(/(.)(.)(.)(.)(.)(.)(.)/g,"$4$5$1$6$7$2$3")
alert("Binny's Cheap Encryption of '"+txt+"' is...\n"+encrypted+
"\nAnd it decryption is...\n"+decrypted)

Here, the replace function will search for the given regular expression and replace it with the string given as the second argument. You can also use this function to replace simple strings.

var txt = document.frm.entry.value
//Replacing
var replaced = txt.replace("Life","Earth")
alert("After replace : " + txt
+"\nAfter replace : " + replaced)

Split a string to create an array

var txt = document.frm.entry.value
var arr = txt.split(" "); //Create an array with all the words as elements
alert("The array is "+arr+"\nThe first word is "+arr[0])