Question

I have been looking for a javascript function that remove duplicate values in array.
I found this function:

function removeDuplicateElement(arrayName)
{
    var newArray=new Array();
    label:for(var i=0; i<arrayName.length;i++ )
    {   
        for(var j=0; j<newArray.length;j++ )
        {
            if(newArray[j]==arrayName[i]) 
            continue label;
        }
        newArray[newArray.length] = arrayName[i];
    }
    return newArray;
}

which is what i need.
Can someone explain me how this function actually work and for what that ‘label:’ is?
I cant understand the logic of this code and if someone can give me an explanation it will be great. 10x

Answer 1

In JavaScript, you can specify a label: as a location to jump to in a continue or break statement. So when the continue is reached, the iteration returns to the outer for loop instead of the inner loop where it resides (which would be the default behavior of continue)

Basically, this function works by making a new array newArray (not modifying the old one) and looping over every element in the original array. It adds the element from the original array to the newArray if not already found. It determines if it already is present in newArray by looping over that it for each iteration of the old array’s loop and looking for the matching value arrayName[i]

function removeDuplicateElement(arrayName)
{
    // Declares a new array to hold the deduped values
    var newArray=new Array();
    // Loops over the original array
    // label: here defines a point for the continue statement to target
    label:for(var i=0; i<arrayName.length;i++ )
    {   
        // Loops over the new array to see if the current value from the old array
        // already exists here
        for(var j=0; j<newArray.length;j++ )
        {
            // The new array already has the current loop val from the old array
            if(newArray[j]==arrayName[i]) 
            // So it returns to the outer loop taking no further action 
            // This advances the outer loop to its next iteration
            continue label;
        }
        // Otherwise, the current value is added to the new array
        newArray[newArray.length] = arrayName[i];
    }
    // The new deduped array is returned from the function
    return newArray;
}

For more information on the function of the continue in this context, have a look at the MDN documentation.