Page 190 - Web Applications (803) Class 12
P. 190
String Operations
You can also use various string methods in JavaScript to work with strings:
Method/ Property Description Example
length Returns the string’s length. document.write(“Welcome”.length)
Output: 7
substring It extracts the substring using the str1 = “Pineapple is very tasty!”;
starting and ending positions as document.write(str1.substring(7,20))
parameters. If you leave the ending Output: le is very ta
position blank, the string will be
extracted from beginning to end.
search returns the position of the first match, var text = “I have a red umbrella”
-1 otherwise var position = text.search(“red”);
Output: 9
document.write(“<br>”+text.
search(“pizza”))
Output: -1
+ Concatenates/joins two strings “Welcome”+ “to” + “Paris”
Output: WelcometoParis
Other Datatypes
It is possible to declare a variable in JavaScript without giving it a value. The variable’s type is undefined if we
do this.
Null, an object of type "object" that denotes a purposeful
non-value.
undefined, an object of type "undefined" denotes an
uninitialised value.
boolean, with values as true or false.
Following these guidelines will enable any given value to be transformed into a boolean:
false, 0, and the empty string (“ “) all become false as well as NaN, null, and undefined.
All alternative values become true.
Notes
When a variable is declared but not given a value, its type is undefined by default.
188 Touchpad Web Applications-XII

