JavaScript Question and Answers
11.How to access an external javascript file that is
stored externally and not embedded?
Ans: This can be achieved by using the following tag between head tags or
between body tags.
<script src="abc.js"></script>
where abc.js is the external javscript file to be accessed.
Q12.What is the difference between an alert box and a
confirmation box?
Ans:An alert box displays only one button which is the OK button whereas the
Confirm box displays two buttons namely OK and cancel.
Q13.What is a prompt box?
Ans:A prompt box allows the user to enter input by providing a text box.
Q14.Can javascript code be broken in different lines?
Ans: Breaking is possible within a string statement by using a backslash \
at the end but not within any other javascript statement.that is ,
document.write("Hello \
world");
is possible but not
document.write \
("hello world"); Q15.How to hide
javascript code from old browsers that dont run it?
Ans:Use the below specified style of comments
<script language=javascript>
<!--
javascript code goes here
// -->
or
Use the <NOSCRIPT>some html code </NOSCRIPT> tags and code the display html
statements between these and this will appear on the page if the browser does
not support javascript. Q16. How
to comment javascript code?
Ans:Use // for line comments and
/*
*/ for block comments
Q17.Name the numeric constants representing max,min values
Ans:Number.MAX_VALUE
Number.MIN_VALUE
Q18.What does javascript null mean?
Ans: The null value is a unique value representing no value or no object.
It implies no object, or null string, no valid boolean value,no number and no
array object. Q19.What does
undefined value mean in javascript?
Ans:Undefined value means the variable used in the code doesnt exist or is
not assigned any value or the property doesnt exist.
Q20.What is the difference between undefined value and
null value?
Ans:
A. Undefined value cannot be explicitly stated that is there is no keyword
called undefined whereas null value has keyword called null
B. typeof undefined variable or property returns undefined whereas typeof null
value returns object
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