Basic JavaScript Interview Questions and Answers

1 :: What are decodeURI() and encodeURI() functions in JavaScript?

Many characters cannot be sent in a URL, but must be converted to their hex encoding. These functions are used to convert an entire URI (a superset of URL) to and from a format that can be sent via a URI.

<script type="text/javascript">
var uri = "http://www.google.com/search?q=Online Web Tutorials at GlobalGuideLine"
document.write("Original uri: "+uri);
document.write("<br />encoded: "+encodeURI(uri));
</script>

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2 :: What's Prototypes for JavaScript?

Objects have "prototypes" from which they may inherit fields and functions.

<script type="text/javascript">
function movieToString() {
return("title: "+this.title+" director: "+this.director);
}
function movie(title, director) {
this.title = title;
this.director = director || "unknown"; //if null assign to "unknown"
this.toString = movieToString; //assign function to this method pointer
}
movie.prototype.isComedy = false; //add a field to the movie's prototype
var officeSpace = new movie("OfficeSpace");
var narnia = new movie("Narni","Andrew Adamson");
document.write(narnia.toString());
document.write("
Narnia a comedy? "+narnia.isComedy);
officeSpace.isComedy = true; //override the default just for this object
document.write("
Office Space a comedy? "+officeSpace.isComedy);
</script>

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3 :: How to create a function using function constructor?

The following example illustrates this
It creates a function called square with argument x and returns x multiplied by itself.
var square = new Function ("x","return x*x");

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4 :: What does break and continue statements do in JavaScript?

Continue statement continues the current loop (if label not specified) in a new iteration whereas break statement exits the current loop in JavaScript.

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5 :: What is eval() in JavaScript?

The eval() method is incredibly powerful allowing us to execute snippets of code during execution in JavaScript.

<script type="text/javascript">
var USA_Texas_Austin = "521,289";
document.write("Population is "+eval("USA_"+"Texas_"+"Austin"));
</script>

This produces
Population is 521,289

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