Compress String using Javascript

compres_string_patterns

function compressStringPatterns(inputStr)
{    
    var inp = inputStr.trim().split(''),    // convert string to an array
        prev='',
        count='',
        out='';

    for(var i = 0; i < inp.length; i++){
// if the prev character is same as the current then incr. the counter
        if(prev === inp[i]){    
            count = count + 1;
        }
        else{ 
//  .. else append the count of the char and the char 
            out = out + count + '' + prev;  
            prev = inp[i];      //  .. reset the prev to the current one
            count = 1;          //  .. initialize the counter
        }
    }
//this is for appending the last count of the character and the character
    out = out + count + '' + prev;  
    return out;
}

console.log( compressStringPatterns( '111223332' ));    //==> 31223312
console.log( compressStringPatterns( '1' ));            //==> 11
console.log( compressStringPatterns( '12' ));           //==> 1112
console.log( compressStringPatterns( '  ' ));           //==> ''