下面给出解决办法。 例 4.1_a function check() { var form = document.getElementById("regForm"); if (form.user.value == "") { alert("用户名不能为空!"); } else { form.submit(); } } 用户 <INPUT TYPE="button" onclick="check();" id="regBut" value="提交"/> 或者用...
It returns a boolean true if a match is found and a boolean false when no match is found. For example: // usage 1: using pure JavaScript document.getElementById('#email').hasAttribute('name'); // usage 2: using jQuery jQuery('#email')[0].hasAttribute('name'); // usage 3:...
log(isEmptyObject(null)); //output: false Advertisement 4. Object.entries() The Object.entries() method returns an array of arrays, with each element being an array of key-value pairs of an object’s property. Let’s go through the following example to understand how it works exactly...
If caused by a click, the clicked element is available as the relatedTarget property of the event. hide.bs.modal This event is fired immediately when the hide instance method has been called. hidden.bs.modal This event is fired when the modal has finished being hidden from the user (will ...
Is null false in JavaScript? Null is not considered false in JavaScript, but it is considered falsy. This means that null is treated as if it’s false when viewed through boolean logic. However, this is not the same thing as saying null is false or untrue. ...
Keeps the tooltip within the bounds of this element. Example: viewport: '#viewport' or { "selector": "#viewport", "padding": 0 } If a function is given, it is called with the triggering element DOM node as its only argument. The this context is set to the tooltip instance. Data at...
push(parseInt(fyl_source[i])); } if(fyl_arr.includes(fyl_new)) { document.querySelector("#msg").innerHTML = fyl_new + "已存在"; } else { fyl_arr.push(fyl_new); } document.getElementById("source").value = fyl_arr; } 12.数组位置用户输入数组, 输入要检索的值, 返回检索到...
exists(x) Check if x exists. This is based on a null, undefined and false check. has.spaces(str) Check if string str has any spaces. has.class(elm, class) Check if element elm has the class name class. has.extension(str, ext) Check if string str has an extension in array ext.ex...
if(!this.readyState||this.readyState==='loaded'||this.readyState==='complete') { //callback在此处执行 js.onload=js.onreadystatechange=null; } }; 3、利用iframe和location.hash 这个办法比较绕,但是可以解决完全跨域情况下的脚步置换问题。原理是利用location.hash来进行传值。在url: http://a.com#...
insertBefore(document.getElementById('myId'), 'before'); // before ... 13.isBrowser:检查是否为浏览器环境 此代码段可用于确定当前运行时环境是否为浏览器。这有助于避免在服务器(节点)上运行前端模块时出错。 const isBrowser = () => ![typeof window, ...