Replace/Add string in textarea in js [closed]

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I have a textarea and some buttons. Onclick of each button I have to do following:

1. Check if textarea contains some text XXX.
2. If contains then remov开发者_C百科e it.
3. If not then add it.

How can I do this in javascript? I have tried following but it does not work:

function addRecip(con){
    var myvalue = document.getElementById("textarea1").value;
    if(myvalue.indexof(con+",")==-1){
        document.getElementById("textarea1").value = myvalue + con + ",";
    } else {
        document.getElementById("textarea1").value = myvalue.replace(con + ",","");
    }
}

---

indexof is actually meant to be spelled indexOf, and JavaScript is case-sensitive.

This works:

function addRecip(con){
    var myvalue = document.getElementById("textarea1").value;
    if(myvalue.indexOf(con+",")==-1){
        document.getElementById("textarea1").value = myvalue + con + ",";
    } else {
        document.getElementById("textarea1").value = myvalue.replace(con + ",","");
    }
}