Edit in JSFiddle

function load(){
    var array1 = [1,2,3,4,5,6,7,8,9];
    var array2 = ['ho', 'ho', 'ho'];
    Array.prototype.splice.apply(array1, 
         [7, array2.length].concat(array2));
    
    
    var element = document.getElementById('finalList');
    
    element.innerText = array1.join(',');
};


load();

<div id='finalList'></div>