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How to check 'undefined' value in jQuery
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when I am testing "typeof obj === undefined", the alert(typeof obj) returning object, even though obj is undefined.
Since obj is type of Object its returning Object, not undefined.
So after hours of testing I opted below technique.
if(document.getElementById(obj) !== null)...
.keyCode vs. .which
...', function(event,handler){
switch(handler.key){
case "ctrl+a":alert('you pressed ctrl+a!');break;
case "ctrl+b":alert('you pressed ctrl+b!');break;
case "r":alert('you pressed r!');break;
case "f":alert('you pressed f!');break;
}
});
hotkeys understands the...
jQuery trigger file input
...cument).ready(function() {
$('#myfile').change(function(evt) {
alert($(this).val());
});
});
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How to check if a query string value is present via JavaScript?
...Just to clarify, this works great if(/[?&]q=/.test(location.search)) { alert("match"); } (I was a bit confused due to @DragosDurlut comment. :)
– Leia
Apr 24 '17 at 4:24
1
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What is JSONP, and why was it created?
...ur page, you define the callback function:
mycallback = function(data){
alert(data.foo);
};
And now, when the script is loaded, it'll be evaluated, and your function will be executed. Voila, cross-domain requests!
It's also worth noting the one major issue with JSONP: you lose a lot of control...
Microbit 板载引脚 · App Inventor 2 中文网
...脚
Microbit_Io_Pin 组件允许用户配置 BBC micro:bit 的模拟引脚用于输入和输出，以及读取、写入和请求 I/O 引脚状态的通知。
更多链接：
RGB LED 控制：示例项目和教程。
读取旋钮状态：示例项目和教程。
读取开关状...
How can I check whether a option already exist in select by JQuery
..."#your_select_id option[value=<enter_value_here>]").length == 0 ){
alert("option doesn't exist!");
}
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jquery get all form elements: input, textarea & select
...select').each(
function(index){
var input = $(this);
alert('Type: ' + input.attr('type') + 'Name: ' + input.attr('name') + 'Value: ' + input.val());
}
);
The below code helps to get the details of elements from all the forms which are place in the loading page,
$('form i...
What is the difference between String.slice and String.substring?
.... Too large values are truncated to the length of the string:
alert ( "testme" .substring (-2)); // "testme", -2 becomes 0
Furthermore, if start > end, the arguments are interchanged, i.e. plot line returns between the start and end:
alert ( "testme" .substring (4, -1)); // "test"
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What exactly does @synthesize do?
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jameshfisher's comment was meant to alert you that you have confused synchronize and synthesize in your answer. You use the two interchangeably.
– Maple
May 10 '16 at 17:32
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