当我尝试向函数传递已传递数组的长度时，为什么会出现错误？

Question

Why do I get error when I try to alert the length of the passed array to the function: Here is code:

<div>
    <button onclick = "CreatTable()">click me!</button>
</div>

<script type ="text/javascript">
        var data = ['First Name', 'Last Name', 'Email'];

        function CreatTable(data) {
        alert(data.length);
}
</script>

In this row:

alert(data.length);

I get this error:

TypeError: data is undefined

Why I get this error? What I am doing wrong?

Answer 1

You are rebinding name data to a function argument. And calling it without any arguments. Sure data is undefined.

function CreatTable() { //use scoped variable data.
        alert(data.length);
}

Answer 2

<div>
    <button onclick = "CreatTable()">click me!</button>
</div>

<script type ="text/javascript">
        var data = ['First Name', 'Last Name', 'Email'];

        function CreatTable() {
            alert(data.length);
        }
</script>

Either pass data as an argument to CreatTable , or remove it and it'll refer to the data array you've defined.

Answer 3

You're calling the function without an argument CreatTable()

whereas your function definition takes data as argument.

Because data is a global variable, just remove it from the function definition:

write function CreatTable() {

instead of

function CreatTable(data) {