$("#param input[type='checkbox']:not('#all')").click(function() {varallcheck=0; $("#param input[type='checkbox']:not('#all')").each(function() {if(!$(this).prop("checked")) { $("#all").prop("checked",false); allcheck=1; } })if(allcheck==0) $("#all").prop("ch...
for example, the attribute has no value or an empty string value. The preferred cross-browser-compatible way to determine if a checkbox is checked is to check for a “truthy” value on the element’s
function checkNullOrUndefined(value) { return value === null || value === undefined; } if (checkNullOrUndefined(someVariable)) { console.log("变量是空值或未定义"); } 遇到问题的原因及解决方法 问题:为什么我的代码在某些情况下仍然报错,即使我已经检查了空值和未定义的值?
if($("#chk1").attr('checked')==undefined) //判断是否已经打勾 单选组 radio: $("input[type=radio]").attr("checked",'2');//设置value=2的项目为当前选中项 下拉框 select: $("#sel").attr("value",'-sel3');//设置value=-sel3的项目为当前选中项 $("11112222").appendTo("#sel...
Calling thejQuery()method withno argumentsreturns an empty jQuery set (with a.lengthproperty of 0). Similarly, if an argument ofnull,undefined, an empty array ([]), or an empty string ("") is passed, the set contains no elements. ...
$.cookie('not_existing'); // => undefined 1. 2. 读取所有Cookie: $.cookie(); // => { "the_cookie": "the_value", "...remaining": "cookies" } 1. 删除Cookie: // 存在返回true并删除,不存在返回false... $.removeCookie('the_cookie'); ...
If you're updating to a newer version of jQuery, be sure to read the release notes published on our blog. If you're coming from a version prior 1.9, you should check out the 1.9 Upgrade Guide as well.Note that this is the API documentation for jQuery core. Other projects have API ...
function(a,b){"object"==typeof module&&"object"==typeof module.exports?module.exports=a.document?b(a,!0):function(a){if(!a.document)throw new Error("jQuery requires a window with a document");return b(a)}:b(a)}("undefined"!=typeof window?window:this,function(a,b){var c=[],...
To check if a field is read-only in jQuery, you can use the .attr() method. This method returns undefined for attributes that have not been set. To check if an input field is read-only, you can use the following code: if ($('#myInput').attr('readonly') !== undefined) { ...
11. // Handle $(""), $(null), or $(undefined) 12. if ( !selector ) { 13. return this; 14. } 15. 16. // Handle $(DOMElement) 17. if ( selector.nodeType ) { 18. this.context = this[0] = selector; 19. this.length = 1; ...