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[Java教程]JS判断输入框值是否为空


<!DOCTYPE html><html><head lang="en">  <meta charset="UTF-8">  <title>JS判断输入框的值是否为空</title></head><body><input type="text" id="txt"/><input type="button" value="检测" id="btn"><script>  var oTxt = document.getElementById('txt');  var oBtn = document.getElementById('btn');  function isnull(val) {    var str = val.replace(/(^\s*)|(\s*$)/g, '');//去除空格;    if (str == '' || str == undefined || str == null) {      //return true;      console.log('空')    } else {      //return false;      console.log('非空');    }  }  oBtn.onclick = function () {    isnull( oTxt.value );  }</script></body></html>