Hi,
How can I prevent duplicate values from getting stored into an array? I am trying to dynamically populate an array with data using the concat() function, but I do not want to allow duplicate selection to be stored in the array. Total noob here. Pls help! Thanks.

Hi amox,

<script>
var entries = new Array("hi","hallo");
var entry = 'hi you';
var found = 0;
for(i=0;i<entries.length;i++){
    if(entries[i] == entry){
        ++found; // value was found
        break;
    }
}
if(found==0)
    entries.push(entry); // save new value
</script>

greetings akratellio

The standard concat() method only puts both arrays together, duplicates as well.
While we could create a function to handle this, it is just as simple to add a method to the Array Object.

Array.concat2();

<script type="text/javascript"> 
// Array.concat2()
// array concatenation method for arrays with duplicates.
// From C and S Design  www.candsdesign.co.uk. 

// define two functions that will become the method 
function checkExist(value,arr) {
for (var zz=0; zz<arr.length; zz++) {
		if ( arr[zz] == value)
		{
			return true;
			break
// leave function and return true if duplicate exists 
		}
}
// otherwise return false 
return false
}

// concatenate both arrays and check for duplicates 
function concat2(testArray,joinArray) {
	for (var zz=0; zz<testArray.length; zz++) {
// pass one array value and the array to join it into 
		if (checkExist(testArray[zz],joinArray) == false) {
// if duplicate is not found push the value onto the join array 
			joinArray.push(testArray[zz]);
		}
	}
}

// create our new function as a method for the Array object		
Array.prototype.concat2 = concat2;
</script>

How to call the new method

<script type="text/javascript"> 
// define and populate two arrays 
Names = new Array("Jack","Jill","Hill","Bucket","Pail","Water");
Arr2 = new Array("Bill","Ben","Little Weed","Bucket","Water","Plant Pot","Rabbit");

// pass both arrays to the method 
Names.concat2(Arr2,Names)
//document.getElementById('content').innerHTML =  Names ;
</script>

Link to demo page Array.Concat2

Thanks a million!!

akratellio,
Useful piece of code! Since I'm using the same function to add items into the array, I tested your code and found out that I couldn't add more values to my array b'cos the variable "found" keeps incrementing. Therefore I modified it a bit. I reinitialize it so it could move on and start over.

if(found==0){
    entries.push(entry); // save new value
}
else{
    //i do something else here
    found=0;
}

Then I can continue to add more items into my array! Thanks!

chrishirst,
I am almost embarassed at your effort to explain the code to me. You went a step further and provided a test page for that! Thank you so much. Accept my bear hug?