js点击选择文本的方法

function selectText() {
  if (document.selection) {
    var range = document.body.createTextRange();
    range.moveToElementText(document.getElementById('copy'));
    range.select();
  } else if (window.getSelection) {
    var range = document.createRange();
    range.selectNode(document.getElementById('copy'));
    window.getSelection().addRange(range);
  }
}