Я сокращаю код (onload Ø):
<input onkeyup="s?e=Date.now():s=Date.now()"onblur="c=this.value.length;this.value+=c/(e-s)"><script>s=0</script>
☑ 113
<input onkeyup="s?e=Date.now():s=Date.now()"onblur="c=this.value.length;this.value+=c/(e-s)">
Ø 93
☑ c=this.value.length;this.value+=c/(e-s)
Ø x=this.value;c=x.length;x+=c/(e-s)