Murk,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script>
window.addEventListener("DOMContentLoaded", function() {
var inp = document.querySelector(".in"),
out = document.querySelectorAll(".out");
inp.addEventListener("input", function(event) {
inp.value.split(/\s+/).forEach(function(text,i) {
out[i] && (out[i].value = text)
});
})
});
</script>
</head>
<body>
<input type="text" class="in">
<input type="text" class="out">
<input type="text" class="out">
<input type="text" class="out">
</body>
</html>