let dom = document.querySelector('textarea')
    dom.onkeydown = function(e){
        console.log(e.key)
        console.log(e.code)
        console.log(e.keyCode)

    if(e.keyCode == 13){
        e.returnValue = false
        console.log('禁用enter事件')
    }
}

<iframe id="pdf" name="pdf" 
      src="static/web/viewer.html?file=compressed.tracemonkey-pldi-09.pdf" 
      style="width:100%; height:500px">
</iframe>

<div id="text">good1230.com-专注于网站排名优化博客建站系统和好文分享</div>

let context = document.getElementById("text")
context.addEventListener('mouseup',() => {
    const selection = window.getSelection()
    const text = selection.toString()
})

字符串转数组split() 函数和数组转字符串join() 函数实例

var string="abcdefg"
console.log(string.split(''));
// 输出结果：["a", "b", "c", "d", "e", "f", "g"]

var array=["a", "b", "c", "d", "e", "f", "g"];
console.log(array.join(','));
// 输出结果：a,b,c,d,e,f,g

JavaScript toFixed() 方法可把Number值四舍五入为指定小数位数的数字。

function format(point) {
  var num = new Number(point);
  return num.toFixed(3)
}
console.log(format('2.236834234'))
// 输出结果 2.237

• <input type="text" oninput="value= value.match(/\d+(\.\d{0,2})?/) ? 
  this.value.match(/\d+(\.\d{0,2})?/)[0] : ''" placeholder="请输入...">