Single line Ace editor

you can use the following code to make editor behave similar to input type="text" (mostly taken from https://github.com/ajaxorg/ace/blob/v1.2.0/demo/kitchen-sink/layout.js#L103)

var el = document.getElementById("textbox")
var editor = ace.edit(el);
editor.setOptions({
    maxLines: 1, // make it 1 line
    autoScrollEditorIntoView: true,
    highlightActiveLine: false,
    printMargin: false,
    showGutter: false,
    mode: "ace/mode/javascript",
    theme: "ace/theme/tomorrow_night_eighties"
});
// remove newlines in pasted text
editor.on("paste", function(e) {
    e.text = e.text.replace(/[\r\n]+/g, " ");
});
// make mouse position clipping nicer
editor.renderer.screenToTextCoordinates = function(x, y) {
    var pos = this.pixelToScreenCoordinates(x, y);
    return this.session.screenToDocumentPosition(
        Math.min(this.session.getScreenLength() - 1, Math.max(pos.row, 0)),
        Math.max(pos.column, 0)
    );
};
// disable Enter Shift-Enter keys
editor.commands.bindKey("Enter|Shift-Enter", "null")

#textbox {
    font-size: 30px;
    border:solid 2px gray;
}
body{
   background: #161619;
   padding: 40px 20px
}

<script src="https://ajaxorg.github.io/ace-builds/src/ace.js"></script>


<div id=textbox>var a = 1</div>

For some reason neither e.preventDefault nor e.stopPropagation works in change event handler. But you can do find-replace.

See fiddle: http://jsfiddle.net/vittore/3rLfdtxb/

 var editor = ace.edit("editor");
 editor.setTheme("ace/theme/monokai");
 editor.getSession().setMode("ace/mode/javascript");
 editor.setFontSize(30)
 editor.getSession().on('change', function(e) {
    console.log(e)
    if (e.data.text.charCodeAt(0) === 10 && e.data.action == "insertText") {
      console.log('cancel event')
      //e.preventDefault() // doesnt work
      //e.stopPropagation()  // doesnt work
      editor.find(String.fromCharCode(10))
      editor.replaceAll(''); // this work
    }
 })

You can even remove if statement from handler and replace line break on any change, regardless.

When you find-replace in change, you got line from cursor to the end of line selected. In order to deselect it after that use :

editor.selection.clearSelection()