JavaScript array [“ index”]。push（）不起作用

Question

<script type="text/javascript">
var ar = [];
ar["index"].push("data1");
ar["index"].push("data2");
ar["index3"].push("data5");
ar[55].push("data7");

console.log(ar);
</script>

I get: TypeError: ar.index is undefined

Answer 1

with this

ar["index"].push("data1");

javascript tries to push "data1" into an array. The problem is that it expects an array, which ar["index"] is not as it is undefined.

You first need to initialize it

ar["index"] = [];
ar["index"].push("data1");

push() documentation here

Answer 2

just make it like

<script type="text/javascript">
var ar = [];
ar.push("data1");
ar.push("data2");
ar.push("data5");
ar.push("data7");

console.log(ar);
</script>

Here is dev reference api => link

Answer 3

Try this :-

<script type="text/javascript">
    var ar = [];
    ar["index"] = data1;
    ar["index"] = data2;
    .........
    ........

    console.log(ar);
</script>

Answer 4

Array accepts the method push

What you wanna do is direct access, like a dictionary style... in this case, setting will just do the trick.

var ar = [];
ar["index"] = "data1";

Answer 5

If you're trying create an array of arrays you must check that the "inner" array exists. Something along the lines of this:

if(ar['index'] == null) {
    ar['index'] = [];
    ar['index'].push("data1");
} else {
 ar['index'].push("data1");
}