检查输入是否为数组，并打印结果

Question

The code is not returning the expected result: I want to return "true" if it is an array on the "checkArray" div and "false" if it is not, depending on the user input.

<input type="text" id="data" placeholder="Insert data">
<button type="submit" onclick="checkArray()">Check</button>
<div id="checkArray"></div>
<script>
function is_array(data) {
    if (data instanceof Array) {
        return true;
    } else {
        return false;
    }
};
function checkArray() {
    var data = document.getElementById("data").value;
    document.getElementById("checkArray").innerHTML = is_array(data);
}

Answer 1

If you are only looking for opening and closing array brackets at the start and end of your input value, you could replace your is_array(data) function with the below code. Although the type of your input value will be string anyway.

function is_array(data) {
    return data[0] + data[data.length - 1] === "[]"
}