Redmine에서 코드 표시에 행 번호 추가(IE 불가)

$(function(){

  // Redmine 3.x
  //const highlightClass='.CodeRay';
  // Redmine 4.x
  const highlightClass = "[class$='syntaxhl']";

  let codeBlocks = document.querySelectorAll( highlightClass );

  let LINE_DELIM_EXP = /\n(?!$)/g;

  Array.prototype.forEach.call(codeBlocks,function( codeBlock ) {

    if (codeBlock.tagName != "CODE") { return; }

    // 行数取得
    let codeLines = codeBlock.innerHTML.split(LINE_DELIM_EXP);
    // 行の桁数
    let figures = String(codeLines.length).length;

    let newCode = '';

    Array.prototype.forEach.call(codeLines , function ( codeLine , index ) {

      // 行番号をつける
      let lineStr = (Array(figures).fill(' ').join('') + ( index + 1 ) ).slice( -1 * figures );
      let lineNumber = document.createElement("span");
      lineNumber.innerHTML = lineStr + ' ';
//      lineNumber.className = 'line-numbers';
      lineNumber.style = 'padding: 2px 4px 2px 4px; background-color: #eee; margin:0px 5px 0px 0px;';

      newCode += lineNumber.outerHTML;
      newCode += codeLine;
      newCode += '\n';
    });
    codeBlock.innerHTML = newCode;

  });
});