Basic JavaScript Interview Preparation Guide

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Solution Is:
<script>
ducument.write(encodeURI(►));
OR
ducument.write(encodeURIComponent(►));
</script>

<script>
document.write("Hello World");
</script>

There are various way to loop through array in JavaScript.

Generic loop:
<script langugage="javascript">
var i;
for (i = 0; i < substr.length; ++i) {
// do something with `substr[i]`
}
</script>

ES5's forEach:
<script langugage="javascript">
substr.forEach(function(item) {
// do something with `item`
});
</script>

jQuery.each:
<script langugage="javascript">
jQuery.each(substr, function(index, item) {
// do something with `item` (or `this` is also `item` if you like)
});
</script>

Functions are objects in JavaScript, as we should know well by now, and as objects, functions have methods, including the powerful Apply, Call, and Bind methods.

// Define the original function.
var checkNumericRange = function (value) {
if (typeof value !== \'number\')
return false;
else
return value >= this.minimum && value <= this.maximum;
}

// The range object will become the this value in the callback function.
var range = { minimum: 10, maximum: 20 };

// Bind the checkNumericRange function.
var boundCheckNumericRange = checkNumericRange.bind(range);

// Use the new function to check whether 12 is in the numeric range.
var result = boundCheckNumericRange (12);
document.write(result);

// Output: true

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>

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>

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");

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

Now create a custom "toString()" method for our movie object. We can embed the function directly in the object like this.
<script type="text/javascript">
function movie(title, director) {
this.title = title;
this.director = director;
this.toString = function movieToString() {
return("title: "+this.title+" director: "+this.director);
}
}
var narnia = new movie("Narni","Andrew Adamson");
document.write(narnia.toString());
</script>
This produces
title: Narni director: Andrew Adamson
Or we can use a previously defined function and assign it to a variable. Note that the name of the function is not followed by parenthisis, otherwise it would just execute the function and stuff the returned value into the variable.
<script type="text/javascript">
function movieToString() {
return("title: "+this.title+" director: "+this.director);
}
function movie(title, director) {
this.title = title;
this.director = director;
this.toString = movieToString;
}
var aliens = new movie("Aliens","Cameron");
document.write(aliens.toString());
</script>
This produces
title: Aliens director: Cameron

Objects can be created in many ways. One way is to create the object and add the fields directly.
<script type="text/javascript">
var myMovie = new Object();
myMovie.title = "Aliens";
myMovie.director = "James Cameron";
document.write("movie: title ""+myMovie.title+""");
<
This produces
movie: title "Aliens"
To create an object write a method with the name of object and invoke the method with "new".
<script type="text/javascript">
function movie(title, director) {
this.title = title;
this.director = director;
}
var aliens = new movie("Aliens","Cameron");
document.write("aliens:"+aliens.toString());
</script>
This produces
aliens:[object Object]

Use an abbreviated format for creating fields using a ":" to separate the name of the field from its value. This is equivalent to the above code using "this.".
<script type="text/javascript">
function movie(title, director) {
title : title;
director : director;
}
var aliens = new movie("Aliens","Cameron");
document.write("aliens:"+aliens.toString());
</script>
This produces
aliens:[object Object]

<script type="text/javascript">
var numbers = ["one", "two", "three", "four"];
numbers.unshift("zero");
document.write(" "+numbers.shift());
document.write(" "+numbers.shift());
document.write(" "+numbers.shift());
</script>

This produces
zero one two
shift, unshift, push, and pop may be used on the same array in JavaScript. Queues are easily implemented using combinations.

The pop() and push() functions turn a harmless array into a stack in JavaScript...

<script type="text/javascript">
var numbers = ["one", "two", "three", "four"];
numbers.push("five");
numbers.push("six");
document.write(numbers.pop());
document.write(numbers.pop());
document.write(numbers.pop());
</script>

This produces
sixfivefour

"join" concatenates the array elements with a specified separator between them in JavaScript.

<script type="text/javascript">
var days = ["Sunday","Monday","Tuesday","Wednesday", "Thursday","Friday","Saturday"];
document.write("days:"+days.join(","));
</script>

This produces
days:Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday

JavaScript does not have a true hashtable object, but through its wierdness, you can use the array as a hashtable.

<script type="text/javascript">
var days = ["Sunday","Monday","Tuesday","Wednesday", "Thursday","Friday","Saturday"];

for(var i=0; i < days.length; i++) {
days[days[i]] = days[i];
}

document.write("days["Monday"]:"+days["Monday"]);
</script>

This produces
days["Monday"]:Monday

The "delete" operator removes an array element in JavaScript , but oddly does not change the size of the array.

<script type="text/javascript">
var days = ["Sunday","Monday","Tuesday","Wednesday", "Thursday","Friday","Saturday"];
document.write("Number of days:"+days.length); delete days[4];
document.write("<br />Number of days:"+days.length);
</script>

This produces
Number of days:7
Number of days:7

The delete operator is used to delete all the variables and objects used in the program ,but it does not delete variables declared with var keyword.

Time inside a date object is stored as milliseconds since Jan 1, 1970 in JavaScript.

e.g.
new Date(06,01,02) // produces "Fri Feb 02 1906 00:00:00 GMT-0600 (Central Standard Time)"
new Date(06,01,02).toLocaleString() // produces "Friday, February 02, 1906 00:00:00"
new Date(06,01,02) - new Date(06,01,01) // produces "86400000"

The Math object contains useful constants such as
Math.PI, Math.E

Math also has a zillion helpful functions in JavaScript.

Math.abs(value); //absolute value
Math.max(value1, value2); //find the largest
Math.random() //generate a decimal number between 0 and 1
Math.floor(Math.random()*101) //generate a decimal number between 0 and 100

The global method, "isNaN()" can tell us about value if a number has gone bad in JavaScript.

var temperature = parseFloat(myTemperatureWidget.value);

if(!isNaN(temperature)) {
alert("Please enter a valid temperature.");
}

We can prepend the number with an empty string in JavaScript

var mystring = ""+myinteger;

//or

var mystring = myinteger.toString();
We can specify a base for the conversion,
var myinteger = 14;
var mystring = myinteger.toString(16);

mystring will be "e".

We can use the parseInt() and parseFloat() methods in JavaScript to convert a string to a number or numeric value. Notice that extra letters following a valid number are ignored, which is kinda wierd but convenient at times.

parseInt("100") ==> 100
parseFloat("98.6") ==> 98.6
parseFloat("98.6 is a common temperature.") ==> 98.6
parseInt("aa") ==> Nan //Not a Number
parseInt("aa",16) ==> 170 //We can supply a radix or base

<script language="JavaScript" type="text/javascript" >
<!--

location.href="http://www.globalguideline.com";

//-->
</script>

To reload the current web page using JavaScript use the below line of code...

window.location.reload(true);