JavaScript Tricks

javascripttricks

Java script programming is client side scripting language.  If you  are doing lot of java script programming. very useful  java script function and tricks.

1.Use the map() function method to loop through an array value

var squares = [1,2,3,4].map(function (val) {
    return val * val;
});
// squares will be equal to [1, 4, 9, 16]

2.Converting JavaScript Array to Comma Separated Value (CSV)

You have a java script array of string or number value and you want to convert it to comma separated values(csv).

Example Code:

var arrayval = ['cat', 'apple', 'oranges', 'chares'];

var string = arrayval .valueOf();

//print string: cat,apple,oranges,chares

The valueOf() method will convert an array in javascript to a comma separated string.


3.Rounding number to N decimal place

var num =5.72121756

num = num.toFixed(4);  // num will be equal to 5.7212

4.Remove Array element by Index

function removeByIndex(arr, index) {
    arr.splice(index, 1);
}

test = new Array();
test[0] = 'Cat';
test[1] = 'Ball';
test[2] = 'bird';
test[3] = 'penguen';

alert("Array before removing elements: "+test);

removeByIndex(test, 2);


alert("Array after removing elements: "+test);

5.Comma operator

var a = 0;
var b = ( a++, 99 );
console.log(a);  // a will be equal to 1

console.log(b);  // b is equal to 99


6. Generate Random number from 1 to N

//random number from 1 to N
var random = Math.floor(Math.random() * N + 1);

//random number from 1 to 10
var random = Math.floor(Math.random() * 10 + 1);

//random number from 1 to 100

var random = Math.floor(Math.random() * 100 + 1);

7.Listbox Select All/Deselect All using JavaScript

function listboxSelectDeselect(listID, isSelect) {
    var listboxs = document.getElementById(listID);
    for(var count=0; count < listboxs.options.length; count++) {
            listboxs.options[count].selected = isSelect;
    }

}


8.Remove Duplicates from JavaScript Array

function removeDuplicates(arr) {
    var temp = {};
    for (var i = 0; i &lt; arr.length; i++)
        temp[arr[i]] = true;
    var r = [];
    for (var k in temp)
        r.push(k);
    return r;
}
//Usage
var fruits = ['apple', 'orange', 'peach', 'apple', 'orange'];
var uniquefruits = removeDuplicates(fruits);
//print uniquefruits ['apple', 'orange', 'peach''];

9. Encode a URL in JavaScript

var encodeurl= 
       "http://example.com/index.html?url=" + encodeURIComponent(myUrl);

10.Serialization and deserialization (working with JSON)

var person = {name :'dev', age : 15, department : {ID : 21, name : "R&D"} }; 
var stringFromPerson = JSON.stringify(person); 
/* stringFromPerson is equal to "{"name":"Sachine","age":31,"department":{"ID":21,"name":"R&D"}}"   */ 
var personFromString = JSON.parse(stringFromPerson);  
/* personFromString is equal to person object  */



Disclaimer: Not all these snippet are written by me. Some of them are collected from other sources on Internet.
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Java script programming is client side scripting language.  If you  are doing lot of java script programming. very useful  java script ...

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