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Single vs Double quotes (' vs ")
...nd tier, as I imagine most people do. For example
<a href="#" onclick="alert('Clicked!');">Click Me!</a>
In that example, you must use both, it is unavoidable.
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Checking if a key exists in a JavaScript object?
...
It will return undefined.
var aa = {hello: "world"};
alert( aa["hello"] ); // popup box with "world"
alert( aa["goodbye"] ); // popup box with "undefined"
undefined is a special constant value. So you can say, e.g.
// note the three equal signs so that null wo...
Get the index of the object inside an array, matching a condition
...",prop2:"qwe"},{prop1:"bnmb",prop2:"yutu"},{prop1:"zxvz",prop2:"qwrq"}]
alert(findIndexInData(data, 'prop2', "yutu")); // shows index of 1
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Capturing “Delete” Keypress with jQuery
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$('html').keyup(function(e){
if(e.keyCode == 46) {
alert('Delete key released');
}
});
Source: javascript char codes key codes from www.cambiaresearch.com
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Checking for a dirty index or untracked files with Git
...mand in a script. For example:
test -z "$(git status --porcelain)" || red-alert "UNCLEAN UNCLEAN"
This effectively says "either there are no changes to be made or set off an alarm"; this one-liner might be preferable to an if-statement depending on the script you are writing.
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Android emulator shows nothing except black screen and adb devices shows “device offline”
...17, the graphics acceleration feature for the emulator is experimental; be alert for incompatibilities and errors when using this feature.
and
Start the AVD Manager and create a new AVD with the Target value of Android 4.0.3 (API Level 15), revision 3 or higher.
So Android 4.0.3 (API Level 1...
Rails: redirect_to with :error, but flash[:error] empty
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As stated in the Rails API only :notice and :alert are by default applied as a flash hash value. If you need to set the :error value, you can do it like this:
redirect_to show_path, flash: { error: "Insufficient rights!" }
...
Javascript call() & apply() vs bind()?
...is is very useful when working with callbacks:
function sayHello(){
alert(this.message);
}
var obj = {
message : "hello"
};
setTimeout(sayHello.bind(obj), 1000);
To achieve the same result with call would look like this:
function sayHello(){
alert(this.message);
}
...
Backbone.View “el” confusion
... "click .btn" : "sayHello",
},
sayHello : function() {
alert("Hello");
},
render : function() {
this.$el.html("<input type='button' class='btn' value='Say Hello'></input>");
}
});
$(function() {
myView = new MyView({el:"#parent_id"});
m...
按键可见性的延时设置 - App Inventor 2 中文网 - 清泛IT社区，为创新赋能！
大家好，咨询请教一个问题， APP上面的 按键 当按下一个按键 设置2号按键可见性为假 （这个功能可以实现），但 在设定时间内，比如一个小时，或者更长时间后， 让原先的2号按键的可见性从原来的假 恢复成真
用“计时...