Document. Log(): "Undefined Is Not a Function"

I know, I know, is a common error and you should look at others and blah blah blah. I have and I could not have found a solution.

This is my ENTIRE code.

<div id="div"></div>

<script>
function item(id, price, name, icon){
    this.id = id;
    this.initPrice = 0;
    this.price = price;
    this.name = name;
    this.icon = icon;

    document.getElementById("div").innerHTML += this.name + " = $" + price + " <input id=\"itemNum" + this.id + "\" onchange=\"item" + this.id + ".calc()\" type=\"number\" style=\"width: 40px;\" value=\"1\"></input><br>";

    this.calc = function(){
        document.log("yay");
    }
}

var item1 = new item(1, 700, "Barrel #1", "");
item1.calc();
</script>

I get the error at line 14 and when I change the input I get the same error at line 14 again. What am I doing wrong? How can I fix this?