如果保存为变量"x"的用户输入不为空或null,我希望此列表只添加列表项并更新计数。然而,addNewItem((和updateCount((函数似乎正在运行,而与输入值无关
const title = document.getElementById('title');
const list = document.getElementById('list');
const input = document.getElementById('todoInput');
const add = document.getElementById('add')
function todoList() {
var x = document.querySelector('#todoInput').value;
function checkInput(){
if (x == null || x == "") {
var p = document.createElement("P")
var emptyError = document.createTextNode("Please enter something for the list");
document.querySelector('#message').appendChild(emptyError);
}
}
checkInput();
function removeMsg() {
const elems = document.querySelector('#message');
setTimeout(function() {
document.querySelector("#message").innerHTML = "";
}, 4000);
}
removeMsg();
if (x !== null || x !== "") {
function addNewItem() {
console.log('something');
const item = input.value;
const text = document.createTextNode(item);
const newItem = document.createElement('li');
const check = document.createElement('span');
check.className = 'circle';
newItem.appendChild(check);
newItem.appendChild(text);
list.appendChild(newItem);
input.value = '';
}
addNewItem();
function updateCount() {
const count = list.childElementCount;
title.innerHTML = `You have ${count} to-dos.`;
}
updateCount();
}
}
todoList();
您可以使用if (x != null && x != "")
检查空值或null值。然而,你也可以这样做:
if(x)
这将确保x的值不仅不为空且不为null,而且还检查所有错误值,如NaN
、undefined
等,并且仅传入truthy的值。