JavaScript replace text in a div element with JQuery Ready

$(document).ready(function(){
replaceButtonText();
});

function replaceButtonText()
{
var buyButtonText = "Buy Now";
var listOfButtonsOnPage = document.getElementsByClassName("listingBuyButton");

for(x=0;x<listOfButtonsOnPage.length;x++)
{
listOfButtonsOnPage[x].innerText = buyButtonText;
}
}