Basic Javascript Array Methods

Understanding some of the basic built-in javascript array methods 

This blog gives a brief overview of the basic javascript methods that are related to arrays.
    
1. concat()

This methods joins two arrays and outputs a new array

<script type="text/javascript">
    //concat()
    var arr1 = [1, 2, 3];
    var arr2 = [4, 5, 6];
    var resultarr = arr1.concat(arr2);
    document.write(resultarr); //Output will be 1,2,3,4,5,6
</script>


2. filter()

This method is used to filter out an array based on some functions. The output will be an array with elements from parent array which satisfies the condition.

<script type="text/javascript">
    //filter()
    var arr1 = ["1", "a", "b", "2", "3"];
    var resultarr = arr1.filter(checkifnumber); //Here we call a function to check whether element is number or not
    document.write(resultarr); //Output will be 1,2,3

    function checkifnumber(element, index, array) {
        return (!isNaN(parseFloat(element)));
    }
</script>

    
3. indexOf()

This method returns the index of the first occurance of an particular element in an array. If element not found in the array, then returns -1.

<script type="text/javascript">
    //indexOf()
    var arr1 = ["1", "a", "b", "2", "3", "b"];
    document.write(arr1.indexOf("b")); //Output will be 2
</script>


4. lastIndexOf()

This method returns the index of the last occurance of an particular element in an array. If element not found in the array, then returns -1.

<script type="text/javascript">
    //lastIndexOf()
    var arr1 = ["1", "a", "b", "2", "3", "b"];
    document.write(arr1.lastIndexOf("b")); //Output will be 5
</script>
    

5. join()

This method joins elements of an array into a string. We can pass a separator as an parameter to join method.

<script type="text/javascript">
    //join()
    var arr1 = ["This", "is", "a", "example", "of", "array", "join"];
    document.write(arr1.join(" ")); //Output will be "This is a example of array join"
    document.write(arr1.join("-")); //Output will be "This-is-a-example-of-array-join"
</script>    


6. reverse()

This method reverses teh order of elements in the array.

<script type="text/javascript">
    //reverse()
    var arr1 = ["a", "b", "c", "d", "e", "f", "g"];
    var resultarr = arr1.reverse(); // It will be  ["g", "f", "e", "d", "c", "b", "a"]
    document.write(resultarr); //Output will be g,f,e,d,c,b,a 
</script>


7. slice()

This method extracts a given number of elements from an array and returns a new array. We can pass begin & end (not included in reulting array) index of elements to be extracted as parameters.

<script type="text/javascript">
    //slice()
    var arr1 = ["a", "b", "c", "d", "e", "f", "g"];
    var resultarr1 = arr1.slice(1, 3); // It will be  ["b", "c"]
    var resultarr2 = arr1.slice(3, 6); // It will be  ["d", "e", "f"]
</script>


8. sort()

This method sorts the elements of an array in an alphabetical order.

<script type="text/javascript">
    //sort()
    var arr1 = ["red", "blue", "white", "green"];
    var resultarr1 = arr1.sort(); // It will be  ["blue", "green", "red", "white"]

    var arr2 = [5, 27, 16, 8];
    var resultarr2 = arr2.sort(3, 6); // It will be  [16, 27, 5, 8]
</script>

Here in the above script, we can find that the numerical array is also sorted in alphabetic order. Inorder to sort it in numerical order, we can wreite a custom function and call it inside our sort function as below.

<script type="text/javascript">
    //sort()
    var arr1 = [5, 27, 16, 8];
    var resultarr1 = arr1.sort(sortNumber); // It will be  [5, 8, 16, 27]

    function sortNumber(num1, num2) {
        return num1 - num2;
    }
</script>


Hope this will be helpful!

Basic Javascript Date Methods

Understanding some of the basic built-in javascript date methods 

This blog gives a brief overview of the basic javascript methods that are related to dates.
    
1. Date()

This method returns current date with time (local date & time).

<script type="text/javascript">
        //Date()
        document.write(Date()); //Output will be current date
</script>


2. getDate()

This method returns current day from an given date.

<script type="text/javascript">
    //getDate()
    var date = new Date();
    document.write(date.getDate()); //Output will be current day

    var date = new Date("Fri Oct 21 2016 14:36:25");
    document.write(date.getDate()); //Output will be 21
</script>


3. getDay()

This method returns the day of a week. Return will be an integer corresponding to particular day. (0 for Sunday, 1 for Monday, etc..)
    
<script type="text/javascript">
    //getDay()
    var date = new Date();
    document.write(date.getDay()); //Output will be index of current day of week

    var date = new Date("Fri Oct 21 2016 14:36:25");
    document.write(date.getDay()); //Output will be 5
</script>
    

4. getFullYear()

This method returns year from a provided date.

<script type="text/javascript">
    //getFullYear()
    var date = new Date();
    document.write(date.getFullYear()); //Output will be current year

    var date = new Date("Fri Oct 23 2015 14:36:25");
    document.write(date.getFullYear()); //Output will be 2015
</script>


5. getMonth()

This method returns month as integer (0 for January, 1 for February, etc..) from a provided date.

<script type="text/javascript">
    //getMonth()
    var date = new Date();
    document.write(date.getMonth()); //Output will be current month

    var date = new Date("Fri Oct 23 2016 14:36:25");
    document.write(date.getMonth()); //Output will be 10
</script>

    
6. getHours()

This method returns hour value from given date.

<script type="text/javascript">
    //getHours()
    var date = new Date();
    document.write(date.getHours()); //Output will be current hour

    var date = new Date("Fri Oct 21 2016 14:36:25");
    document.write(date.getHours()); //Output will be 14
</script>
    

7. getMinutes()

This method returns minute value from given date.

<script type="text/javascript">
    //getMinutes()
    var date = new Date();
    document.write(date.getMinutes()); //Output will be current minute

    var date = new Date("Fri Oct 21 2016 14:36:25");
    document.write(date.getMinutes()); //Output will be 36
</script>


8. getSeconds()

This method returns seconds value from given date.

<script type="text/javascript">
    //getSeconds()
    var date = new Date();
    document.write(date.getSeconds()); //Output will be current seconds value

    var date = new Date("Fri Oct 21 2016 14:36:25");
    document.write(date.getSeconds()); //Output will be 25
</script>

Hope this will be helpful!

Basic Javascript Number Methods

    Understanding some of the basic built-in javascript number methods

    This blog gives a brief overview of the basic javascript methods that are related to numbers.

    1. isNaN()

    Check whether a value is a number and returns true if not a number (NaN stands for Not a Number)
 
 <script type="text/javascript">
        //isNaN()
        document.write(isNaN(25)); //Output is false
        document.write(isNaN("This is a string")); //Output is true
        document.write(isNaN("77")); //Output is false
        document.write(isNaN("05/10/2016")); //Output is true
    </script>


    2. parseInt()

    Converts a string to an Integer. If string doesn't start with a valid number, it returns NaN

 <script type="text/javascript">
        //parseInt()
        document.write(parseInt(25)); //Output is 25
        document.write(parseInt("This is a string")); //Output is NaN
        document.write(parseInt("77.56")); //Output is 77
        document.write(parseInt("05/10/2016")); //Output is 5
    </script>


    3. parseFloat()
 
    Converts a string to an Float value. If string doesn't start with a valid number, it returns NaN

 <script type="text/javascript">
        //parseFloat()
        document.write(parseFloat(25)); //Output is 25
        document.write(parseFloat("This is a string")); //Output is NaN
        document.write(parseFloat("77.56")); //Output is 77.56
        document.write(parseFloat("05/10/2016")); //Output is 5
    </script>

 
    4. toFixed()

    Converts a number to a decimal value with specified number of digits after the decimal point.

  <script type="text/javascript">
        //toFixed()
        document.write((25).toFixed(2)); //Output is 25.00
        document.write((25.58).toFixed(2)); //Output is 25.58
        document.write((25.52).toFixed(3)); //Output is 25.520
        document.write((25.4578).toFixed(3)); //Output is 25.458
    </script>


    5. toString()

    Converts a number to a string.

<script type="text/javascript">
        //toString()
        document.write((25).toString()); //Output is 25
        document.write((25.58).toString()); //Output is 25.58
        document.write((25 + 50).toString()); //Output is 75
        document.write((25.52 + 24.64).toString()); //Output is 50.16
    </script>


    6. isFinite()

    Checks whether if a number is a finite number and returns true or false accordingly

 <script type="text/javascript">
        //isFinite()
        document.write(isFinite(25)); //Output is true
        document.write(isFinite("This is a string")); //Output is false
        document.write(isFinite("77")); //Output is true
        document.write(isFinite("05/10/2016")); //Output is false
    </script>

 
    7. toPrecision()

    Converts a number to a decimal number string with total digits (digits on left and right of decimal point) as specified.

  <script type="text/javascript">
        //toPrecision()
        document.write((2).toPrecision(2)); //Output is 2.0
        document.write((25.58).toPrecision(2)); //Output is 26
        document.write((25.52).toPrecision(3)); //Output is 25.5
        document.write((25.4578).toPrecision(4)); //Output is 25.46
    </script>


    Hope this will be helpful!