TextBoxの編集モードでカーソル行の上下複製

code:script.js

function copyUpLine(e, obj){

//オプション+上で行を上に複製

if(!(e.altKey && e.shiftKey && e.keyCode === 38) ){ return; }

e.preventDefault();

const selectpoint = obj.selectionStart;

const textbody = obj.value;

const arry = textbody.split('\n');

const textbefore = obj.value.substr(0, obj.selectionStart) ;

const currentLine = (textbefore.match( /\n/g ) || [] ).length;

const tempN = arrycurrentLine ;//もともとの行を保存

arry.splice(currentLine,0,tempN);

obj.value = arry.join('\n');

obj.setSelectionRange(selectpoint,selectpoint);

}