Uncaught TypeError: Cannot read properties of undefined (reading ‘className‘)这个报错如何解决

首先这个报错是指传入的参数没有内容为undefined，需要加判断当传入的值为undefined时执行什么操做，

代码演示

function openTab(evt, tabName) {
  var i, tabcontent, tablinks;
  tabcontent = document.getElementsByClassName("tabcontent");
   console.log(tabcontent);
  for (i = 0; i < tabcontent.length; i++) {
    tabcontent[i].style.display = "none";
  }
  tablinks = document.getElementsByClassName("tablinks");
  console.log(tablinks);
  for (i = 0; i < tablinks.length; i++) {
	tablinks[0].className.replace("active");
    tablinks[i].className = tablinks[i].className.replace(" active", "");
  }
  document.getElementById(tabName).style.display = "block";
  evt.currentTarget.className += " active";
  // console.log(i);
  // console.log(tabcontent);
  // console.log(tablinks);
}
fu()
function fu(){
	openTab("",'tab1')
}


	
}

当fu()函数执行时openTab(evt, tabName)中evet为空

正确写法

function openTab(evt, tabName) {
	if(evt==''){
		
	}else{
		var i, tabcontent, tablinks;
		tabcontent = document.getElementsByClassName("tabcontent");
		 console.log(tabcontent);
		for (i = 0; i < tabcontent.length; i++) {
		  tabcontent[i].style.display = "none";
		}
		tablinks = document.getElementsByClassName("tablinks");
		console.log(tablinks);
		for (i = 0; i < tablinks.length; i++) {
			tablinks[0].className.replace("active");
		  tablinks[i].className = tablinks[i].className.replace(" active", "");
		}
		document.getElementById(tabName).style.display = "block";
		evt.currentTarget.className += " active";
		// console.log(i);
		// console.log(tabcontent);
		// console.log(tablinks);
	}
 
}
fu()
function fu(){
	openTab("",'tab1')

	
}

需要加一个event为空的判断。

希望可以帮助大家；