<body contenteditable=true>x   y
<script>
document.body.firstChild.splitText(2)  // "x " and "  y"
                        .splitText(1)  // "x", " " and "  y"
                        .splitText(1); // "x", "", " " and "  y"
getSelection().collapse(document.body, 1);
document.execCommand("forwardDelete");
</script>
