単語表で置換

var list = "apple, りんご, orange, みかん, orangejuice, おれんじじゅーす";
// ↑をカンマ区切りで設定してね

var dict = list.split(/\s*,\s*/);
if (dict.length % 2 != 0) { throw new Error("単語数が奇数になってる"); }
for (var i = 0; i < dict.length / 2; i++) { dict[i] = [dict[i * 2].replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&'), dict[i * 2 + 1]]; }
dict.length /= 2;
dict.sort(function(a, b) { return b[0].length - a[0].length; });
if (document.selection.Text == "") { document.selection.SelectAll(); }
var text = document.selection.Text;
for (var i = 0; i < dict.length; i++) { text = text.replace(dict[i][0], dict[i][1]); }
document.selection.Text = text;