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Usage of javascript:void(0) means that the author of the HTML is misusing the anchor element in place of the button element. Anchor tags are often abused with the onclick event to create pseudo-buttons by setting href to "#" or "javascript:void(0)" to prevent the page from refreshing. These values cause unexpected behavior when copying/dragging ...
void 0 will always return undefined. undefined, on the other hand, can be whatever Mr. JavaScript decides he wants it to be. Why void 0, specifically? Why should we use void 0? What's so special about 0? Couldn't we just as easily use 1, or 42, or 1000000 or "Hello, world!"? And the answer is, yes, we could, and it would work just as well.
The void operator is often used merely to obtain the undefined primitive value, usually using “void(0)” (which is equivalent to “void 0”). In these cases, the global variable undefined can be used instead (assuming it has not been assigned to a non-default value).
2. void(0) void 是 JavaScript 中的一个运算符，它会对其参数求值，然后返回 undefined。常见的形式是 void(0)，其中 0 是参数，但参数可以是任意表达式。 这里的 void(0) 通常用来明确表示“什么都不返回”。换句话说，这是一种用来阻止页面跳转的常见方法。 综合解释：
The void operator evaluates the given expression and then returns undefined. The void operator is often used merely to obtain the undefined primitive value, usually using “void(0)” (which is equivalent to “void 0”). In these cases, the global variable undefined can be used instead (assuming it has not been assigned to a non-default value).
Where as void 0 is void 0 anywhere. Anyways, this technique will surely confuse the JITs which already optimize undefined (FF, Chrome but not IE10) because it's a global constant and even static analysis can see if it's shadowed. With this, you turn it into a normal variable look-up and it's not a compile-time constant for sure. Of course that ...
Which implies, strictly speaking, that (void*)0 is a null pointer constant, but ((void*)0) is not. Then: I'm sure that most C implementations do treat a parenthesized null pointer constant as a null pointer constant, and define NULL either as 0, ((void*)0), or in some other manner. The two referenced sections say: § 6.3.2.3
href = "javascript:void(0);" добавляют, чтобы при нажатии на ссылку, которая выполняет не свою прямую функцию, страница не прокручивалась вверх, а всё оставалось на месте
Почему именно void 0? Это только традиция; void 0 - простой и короткий код. Другие варианты, такие как void 9 и void "привет", тоже работают.
javascript:undefined; javascript:void 0; javascript: With the exception that undefined can be overridden by declaring a variable with the same name. Use of void 0 is generally pointless, and it's basically been whittled down from void functionThatReturnsSomething().