Javascript, Multiselect copy to textarea-CodePudding

I want to copy multiselect options to textarea. I wrote code and it goes well up till I change value in textarea box for example when I add something. After adding additionaly characters to textarea JS coping function don't work. Why? This is code:

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>

<form >
    <div >
        <div >Multiselect:<br/>
            <select id="source_select" multiple="multiple" style="width: 500px; height:200px">
                <option value="option 1"> option 1 </option>
                <option value="option 2"> option 2 </option>
                <option value="option 3"> option 3 </option>
                <option value="option 4"> option 4 </option>
                <option value="option 5"> option 5 </option>
            </select>
        </div>
        <div ><br/><br/>Textarea:<br/>
            <textarea name="text_to_db" id="target_textarea"  style="width: 500px; height:200px"></textarea>
        </div>
    </div>
    <div >
        <div ><br/>
            <button type="button" onclick="myFunction()">Copy multiselect to textarea</button>
        </div>
    </div>
</form>

<script>
function myFunction() {
            if (document.getElementById("source_select").length > 0) {
                for (let i=0; i < document.getElementById("source_select").length; i  ){
                    const option = document.getElementById("source_select").options[i];
                    const value = option.value;
                    if (option.selected) {
                        let nowy_tekst = document.getElementById("target_textarea").innerHTML   value   ", ";
                        document.getElementById("target_textarea").innerHTML = nowy_tekst;
                       // option.remove();
                    }
                }
            }
}
</script>
</body>
</html>

CodePudding user response：

You should use .value instead of .innerHTML since textarea is a form element.

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>

<form >
    <div >
        <div >Multiselect:<br/>
            <select id="source_select" multiple="multiple" style="width: 500px; height:200px">
                <option value="option 1"> option 1 </option>
                <option value="option 2"> option 2 </option>
                <option value="option 3"> option 3 </option>
                <option value="option 4"> option 4 </option>
                <option value="option 5"> option 5 </option>
            </select>
        </div>
        <div ><br/><br/>Textarea:<br/>
            <textarea name="text_to_db" id="target_textarea"  style="width: 500px; height:200px"></textarea>
        </div>
    </div>
    <div >
        <div ><br/>
            <button type="button" onclick="myFunction()">Copy multiselect to textarea</button>
        </div>
    </div>
</form>

<script>
function myFunction() {
            if (document.getElementById("source_select").length > 0) {
                for (let i=0; i < document.getElementById("source_select").length; i  ){
                    const option = document.getElementById("source_select").options[i];
                    const value = option.value;
                    if (option.selected) {
                        let nowy_tekst = document.getElementById("target_textarea").value   value   ", ";
                        document.getElementById("target_textarea").value = nowy_tekst;
                       // option.remove();
                    }
                }
            }
}
</script>
</body>
</html>